Airline Traffic Data

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January 2018 U.S. Airline Traffic Data

Release Number: 
BTS 19-18

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U.S. airlines’ January systemwide (domestic and international) scheduled service passenger enplanements fell to 71.6 million, 0.8 percent fewer than December, seasonally-adjusted, after growing three consecutive months from October 2017 to December 2017 (Table 1).

Enplanements in millions (Seasonally Adjusted)
Enplanements in millions (Seasonally Adjusted)
Jan-1564.8
Feb-1565.1
Mar-1565.7
Apr-1565.7
May-1566.0
Jun-1566.3
Jul-1566.9
Aug-1567.4
Sep-1567.2
Oct-1567.9
Nov-1567.4
Dec-1567.9
Jan-1667.7
Feb-1667.8
Mar-1667.2
Apr-1667.9
May-1668.9
Jun-1669.1
Jul-1668.3
Aug-1668.0
Sep-1669.2
Oct-1669.1
Nov-1669.4
Dec-1669.5
Jan-1769.7
Feb-1769.7
Mar-1770.1
Apr-1770.5
May-1771.1
Jun-1771.1
Jul-1771.7
Aug-1771.4
Sep-1768.0
Oct-1772.0
Nov-1772.1
Dec-1772.2
Jan-1871.6

In seasonally-adjusted numbers, from December 2017 to January 2018, enplanements on domestic flights declined 1.0 percent while enplanements on U.S. airlines’ international flights to and from the U.S. were virtually unchanged, resulting in a 0.8 percent systemwide decline (Tables 1, 2, 3).

In one year, from January 2017 to January 2018, enplanements on domestic flights increased 2.8 percent while enplanements on U.S. airlines’ international flights to and from the U.S. rose 1.8 percent, resulting in a 2.7 percent systemwide increase (Tables 1, 2, 3).

In three years, from January 2015 to January 2018, enplanements on domestic flights increased 10.9 percent while enplanements on U.S. airlines’ international flights to and from the U.S. rose 7.3 percent, resulting in a 10.5 percent systemwide increase (Tables 1, 2, 3).

In unadjusted numbers, systemwide, domestic and international enplanements all reached highs for the month of January (Tables 13, 14, 15).

Trends (Percent changes based on unrounded numbers)

Seasonally-adjusted

Systemwide passenger enplanements (71.6 million) were down 0.8 percent from the all-time seasonally-adjusted high (72.2 million) reached in December 2017 (Table 1). Domestic passenger enplanements (62.5 million) were down 1.0 percent from the all-time seasonally-adjusted high (63.1 million) reached in December 2017 (Table 2). International passenger enplanements (9.0 million) were down 0.9 percent from the all-time seasonally-adjusted high (9.1 million) reached in April 2017 (Table 3).           

Systemwide revenue passenger miles (RPMs) (81.5 billion) were down 0.3 percent from the all-time seasonally-adjusted high (81.7 billion) reached in November 2017 (Table 4). Domestic RPMs (57.9 billion) were down 0.4 percent from the all-time seasonally-adjusted high (58.2 billion) reached in November 2017 (Table 5). International RPMs (23.5 billion) were down 0.9 percent from the all-time seasonally-adjusted high (23.8 billion) reached in April 2017 (Table 6).

Systemwide available seat-miles (ASMs) (98.0 billion) reached a new seasonally-adjusted all-time high, up 0.3 percent from the previous high in December 2017 (97.7 billion) (Table 7). Domestic ASMs (68.8 billion) reached a new seasonally-adjusted all-time high, up 0.3 percent from the previous high in December 2017 (68.6 billion) (Table 8). International ASMs (29.2 billion) were virtually unchanged from the all-time seasonally-adjusted high (29.2 billion) reached in October 2017 (Table 9).

Systemwide load factor (83.1) was down 1.7 points from the all-time seasonally-adjusted high (84.7) reached in October 2015 (Table 10). Domestic load factor (84.2) was down 1.6 points from the all-time seasonally-adjusted high (85.8) reached in October 2015 (Table 11). International load factor (80.6) was down 2.5 points from the all-time seasonally-adjusted high (83.1) reached in March 2013 (Table 12).

Load factor is a measure of the use of aircraft capacity that compares the system use, measured in RPMs as a proportion of system capacity, measured ASMs.

The seasonally-adjusted load factor fell from December (83.4) to January (83.1) as a result of no change in RPMs from December to January combined with a 0.3 percent increase in ASMs (Tables 4, 7).

Seasonally-adjusted trends are for the time period January 2000 to present. Additional data, including domestic and international numbers, can be found on the seasonally-adjusted data  page.

Unadjusted

Systemwide passenger enplanements (64.3 million) reached an all-time January high, up 2.7 percent from the previous high (62.6 million) reached in 2017 (Table 13). Domestic passenger enplanements (55.7 million) reached an all-time January high, up 3.0 percent from the previous high (54.1 million) reached in 2017 (Table 14). International passenger enplanements (8.6 million) reached an all-time January high, up 1.0 percent from the previous January high (8.5 million) reached in 2017 (Table 15).

Enplanements in millions (Unadjusted)
Enplanements in millions (Unadjusted)
Jan-1455.8
Feb-1452.4
Mar-1466.4
Apr-1463.5
May-1466.5
Jun-1468.6
Jul-1471.9
Aug-1469.5
Sep-1460.0
Oct-1464.5
Nov-1459.7
Dec-1463.8
Jan-1557.8
Feb-1554.2
Mar-1568.2
Apr-1565.9
May-1568.9
Jun-1571.3
Jul-1575.6
Aug-1572.9
Sep-1563.7
Oct-1568.7
Nov-1564.6
Dec-1566.4
Jan-1660.8
Feb-1658.5
Mar-1670.6
Apr-1667.2
May-1671.5
Jun-1674.5
Jul-1676.9
Aug-1673.5
Sep-1666.5
Oct-1669.5
Nov-1666.6
Dec-1668.0
Jan-1762.6
Feb-1758.4
Mar-1773.0
Apr-1770.3
May-1773.7
Jun-1777.0
Jul-1779.8
Aug-1777.1
Sep-1764.9
Oct-1772.7
Nov-1769.6
Dec-1770.3
Jan-1864.3

Systemwide RPMs (73.3 billion) reached an all-time January high, up 2.6 percent from the previous high (71.4 billion) reached in 2017 (Table 16). Domestic RPMs (51.7 billion) reached an all-time January high, up 3.1 percent from the previous high (50.1 billion) reached in 2017 (Table 17). International RPMs (21.6 billion) reached an all-time January high, up 1.6 percent from the previous high (21.3 billion) reached in 2017 (Table 18).

Systemwide ASMs (93.0 billion) reached an all-time January high, up 3.4 percent from the previous high (90.0 billion) reached in 2017 (Table 19). Domestic ASMs (65.5 billion) reached an all-time January high, up 3.9 percent from the previous high (63.1 billion) reached in 2017 (Table 20). International ASMs (27.5 billion) reached an all-time January high, up 2.3 percent from the previous high (26.9 billion) reached in 2017 (Table 21).

Systemwide load factor (78.8) was down 1.5 points from the all-time January high (80.3) reached in 2014 (Table 22). Domestic load factor (78.9) was down 1.8 points from the all-time January high (80.7) reached in 2014 (Table 23). International load factor (78.7) was down 0.9 points from the all-time January high (79.6) reached in 2014 (Table 24).           

Unadjusted trends are for the time period January 1996 to present. Data are available at Customize Table and can be downloaded from the seasonally-adjusted data  page.

Explanation of seasonal adjustment

When the primary purpose is to examine monthly shifts in transportation services output and analyze short-term trends, the variation introduced by normal seasonal changes must be removed from the data. Transportation is highly seasonal, and without adjustment, the data do not give an accurate picture of underlying changes in aviation, passenger travel.

Seasonal adjustment of the data removes the seasonal events that follow a regular seasonal pattern. Changes that are not due to seasonality, such as a change in air travel resulting from economic conditions become more readily apparent.

The aviation data are seasonally adjusted for the effects of trading day, moving holidays, and data outliers.

See Seasonal Adjustment for methodology and additional explanation.

Reporting Notes

Data are compiled from monthly reports filed with BTS by commercial U.S. air carriers detailing operations, passenger traffic and freight traffic. This release includes data received by BTS from 78 carriers as of April 3 for U.S. carrier scheduled civilian operations.

Go to the complete list of reporting and non-reporting carriers. U.S. carriers’ foreign point-to-point flights are included in system and international totals. To create a customized table for passengers, flights, RPMs, ASMs and other data, including non-scheduled service, go to https://www.transtats.bts.gov/TRAFFIC/

For additional scheduled service numbers for U.S. and foreign airlines, by airline and by airport, see Passengers, Flights, Revenue Passenger-Miles, Available Seat-Miles and Load Factor.

Traffic numbers are available on the BTS website at TranStats.  Click on “Aviation.”  For systemwide passengers, RPMs and ASMs by carrier through January, click on “Air Carrier Summary Data (Form 41 and 298C Summary Data),” and then click on “Schedule T-1.” Use crosstabs to find scheduled service.

For domestic numbers through January and international numbers through October by origin as well as by carrier, click on “Aviation,” then click on “Air Carrier Statistics (Form 41 Traffic).” Click on “T-100 Market” for system passenger numbers, “T-100 Domestic Market” for domestic or “T-100 International Market” for international. For flights, stage length and trip length, use the appropriate T-100 Segment database. Use crosstabs to find scheduled service.

International totals in this press release consist of all U.S. carrier operations to and from the U.S. and from one foreign point to another foreign point. TranStats T-100 systemwide and international totals do not include U.S. carriers’ foreign point-to-point flights. For January, U.S. carriers reported 38,037 foreign point-to-point passengers.

Data are subject to revision. BTS has scheduled May 10 for the release of February traffic data. None of the data are from samples so measures of statistical significance do not apply.


Seasonally-Adjusted Tables

Passenger Enplanements on U.S. Airlines, Seasonally-Adjusted (Tables 1-3)

Systemwide (Domestic + International) passenger enplanements (seasonally-adjusted) in millions (000,000), Scheduled service only
2015201620172018
January64.8067.6969.7171.57
February65.0867.7769.73
March65.6967.1870.09
April65.7567.9570.54
May65.9968.8771.08
June66.2769.1171.15
July66.8768.3171.66
August67.4468.0471.40
September67.2569.2167.99
October67.8669.1272.03
November67.3969.3872.10
December67.8869.4872.17
Source: 

Bureau of Transportation Statistics, T-100 Market

Domestic passenger enplanements on U.S. airlines (seasonally-adjusted) in millions (000,000), Scheduled service only
2015201620172018
January56.3859.0460.8362.53
February56.6459.1160.90
March57.2758.5561.22
April57.4359.4261.42
May57.5760.2961.99
June57.8060.4162.04
July58.3259.6662.55
August58.8159.4462.33
September58.6260.5659.43
October59.2260.4463.02
November58.7660.7463.06
December59.2260.6263.13
Source: 

Bureau of Transportation Statistics, T-100 Domestic Market

International passenger enplanements (seasonally-adjusted) in millions (000,000), Scheduled service only
2015201620172018
January8.428.658.889.04
February8.448.668.83
March8.438.648.86
April8.328.539.12
May8.438.589.09
June8.488.719.11
July8.558.649.11
August8.638.619.07
September8.638.658.56
October8.638.689.01
November8.648.659.04
December8.668.869.04
Source: 

Bureau of Transportation Statistics, T-100 International Market

Revenue Passenger-Miles on U.S. Airlines, Seasonally-Adjusted (Tables 4-6)

Systemwide (Domestic + International) RPMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January73.276.679.381.5
February73.676.978.7
March74.576.479.5
April74.077.180.4
May74.677.780.6
June74.978.280.9
July75.677.781.4
August76.177.181.2
September75.978.377.9
October76.878.281.5
November76.278.581.7
December77.078.981.5
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic RPMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January50.753.856.357.9
February51.154.155.7
March51.953.856.4
April51.954.556.7
May52.155.257.1
June52.455.457.3
July52.854.857.8
August53.254.657.6
September53.155.454.9
October53.855.458.1
November53.555.758.2
December54.255.858.0
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

International RPMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January22.522.823.023.5
February22.522.723.0
March22.622.723.1
April22.122.623.8
May22.522.623.5
June22.522.823.6
July22.822.923.5
August22.922.623.6
September22.822.923.0
October22.922.823.4
November22.722.723.6
December22.823.123.5
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Available Seat-Miles on U.S. Airlines, Seasonally-Adjusted (Tables 7-9)

Systemwide (Domestic + International) ASMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January88.291.495.098.0
February87.692.194.9
March88.792.695.2
April89.492.595.7
May89.793.196.0
June89.593.296.8
July90.393.397.3
August90.693.597.3
September90.694.095.4
October90.693.397.5
November91.193.597.2
December91.594.397.7
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic ASMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January60.463.366.568.8
February59.964.066.4
March60.964.466.6
April61.564.366.8
May61.864.867.0
June61.665.067.7
July62.265.168.2
August62.465.368.3
September62.465.666.6
October62.765.168.3
November63.265.768.1
December63.365.968.6
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

International ASMs (seasonally-adjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January27.828.128.529.2
February27.728.128.6
March27.828.228.6
April27.928.128.9
May27.928.329.0
June27.828.329.1
July28.128.229.1
August28.228.329.0
September28.228.328.7
October27.828.229.2
November27.927.729.0
December28.228.429.1
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Load Factor on U.S. Airlines, Seasonally-Adjusted (Tables 10-12)

Systemwide (Domestic + International) RPMs/ASMs (both seasonally-adjusted) in percent, Scheduled service only
2015201620172018
January82.983.883.583.1
February84.083.582.9
March83.982.683.5
April82.883.384.0
May83.283.584.0
June83.783.983.6
July83.883.283.7
August84.082.583.4
September83.883.381.7
October84.783.883.6
November83.683.984.1
December84.183.683.4
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic RPMs/ASMs (both seasonally-adjusted) in percent, Scheduled service only
2015201620172018
January83.985.184.684.2
February85.284.683.9
March85.283.584.7
April84.484.784.8
May84.385.185.2
June85.085.384.6
July84.984.284.8
August85.283.684.3
September85.184.482.3
October85.885.185.1
November84.684.885.4
December85.784.684.6
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment

International RPMs/ASMs (both seasonally-adjusted) in percent, Scheduled service only
2015201620172018
January80.881.080.980.6
February81.480.880.6
March81.280.480.8
April79.380.282.3
May80.979.981.1
June80.780.781.2
July81.381.081.0
August81.479.881.4
September81.080.880.2
October82.380.980.1
November81.481.981.2
December80.781.280.6
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment

Unadjusted Tables

 

Passenger Enplanements on U.S. Airlines, Unadjusted (Tables 13-15)

Systemwide (Domestic + International) passenger enplanements (unadjusted) in millions (000,000), Scheduled service only
2015201620172018
January57.7860.8162.6264.33
February54.1658.5058.38
March68.2070.5672.96
April65.9267.2470.26
May68.9371.5273.68
June71.2774.5077.01
July75.6376.8979.82
August72.8773.4577.10
September63.7466.4864.92
October68.7369.5472.70
November64.5966.5969.63
December66.4067.9870.33
1 Mo. Total57.7860.8162.6264.33
Yr. Total798.22824.06849.41
Source: 

Bureau of Transportation Statistics, T-100 Market

Domestic passenger enplanements (unadjusted) in millions (000,000), Scheduled service only
2015201620172018
January49.7352.4754.1155.74
February47.1751.1151.08
March59.5661.5963.96
April57.7058.8961.10
May60.2562.7564.44
June61.8164.7666.75
July65.1366.1468.58
August62.7763.5066.67
September55.9958.6257.15
October60.8961.7164.62
November57.1559.2761.91
December57.8759.1861.37
1 Mo. Total49.7352.4754.1155.74
Yr. Total696.02719.99741.74
Source: 

Bureau of Transportation Statistics, T-100 Domestic Market

International passenger enplanements (unadjusted) in millions (000,000), Scheduled service only
2015201620172018
January8.068.338.518.60
February7.007.397.30
March8.648.969.00
April8.228.349.16
May8.678.769.24
June9.469.7410.26
July10.5010.7511.24
August10.099.9510.44
September7.757.867.77
October7.847.838.08
November7.447.327.72
December8.538.818.96
1 Mo. Total8.068.338.518.60
Yr. Total102.20104.04107.68
Source: 

Bureau of Transportation Statistics, T-100 International Market

Revenue Passenger-Miles on U.S. Airlines, Unadjusted (Tables 16-18)

Systemwide (Domestic + International) RPMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January66.069.371.473.3
February59.864.664.3
March75.878.780.8
April73.175.179.5
May78.080.883.5
June82.786.589.7
July88.390.694.1
August85.286.190.4
September72.575.374.7
October76.177.380.6
November70.072.275.7
December74.877.079.6
1 Mo. Total66.069.371.473.3
Yr. Total902.2933.5964.4
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic RPMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January45.148.150.151.7
February42.346.546.5
March53.956.758.8
April51.953.656.3
May54.357.159.0
June57.060.362.5
July60.462.465.0
August57.859.362.5
September49.952.751.9
October54.155.358.3
November50.953.355.9
December53.154.857.0
1 Mo. Total45.148.150.151.7
Yr. Total630.7660.0683.8
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

 Bureau of Transportation Statistics, T-100 Segment

International RPMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January20.821.221.321.6
February17.518.117.8
March21.822.022.1
April21.221.523.2
May23.823.724.5
June25.726.227.2
July27.828.329.1
August27.426.927.9
September22.622.722.8
October22.022.022.4
November19.118.919.8
December21.722.222.7
1 Mo. Total20.821.221.321.6
Yr. Total271.6273.5280.6
Notes: 

Revenue passenger-miles are a measure of the volume of air passenger transportation. A revenue passenger-mile is equal to one paying passenger carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Available Seat-Miles on U.S. Airlines, Unadjusted (Tables 19-21)

Systemwide (Domestic + International) ASMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January83.486.390.093.0
February74.582.081.4
March90.394.296.8
April88.691.694.8
May92.896.499.5
June95.799.9103.7
July101.0104.4108.6
August98.6101.8105.8
September87.390.491.4
October89.592.296.4
November84.986.990.3
December90.393.096.3
1 Mo. Total83.486.390.093.0
Yr. Total1,076.91,119.11,155.0
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic ASMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January57.059.763.165.5
February51.357.557.4
March62.966.568.7
April61.163.866.1
May63.466.568.8
June65.268.871.7
July68.671.574.8
August66.770.073.2
September59.562.563.1
October62.664.868.0
November60.562.965.1
December63.265.768.2
1 Mo. Total57.059.763.165.5
Yr. Total742.0780.2808.2
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

International ASMs (unadjusted) in billions (000,000,000), Scheduled service only
2015201620172018
January26.426.726.927.5
February23.324.523.9
March27.527.728.0
April27.527.828.7
May29.429.830.6
June30.531.132.0
July32.432.933.8
August31.931.932.6
September27.827.928.3
October27.027.428.4
November24.524.025.1
December27.027.328.0
1 Mo. Total26.426.726.927.5
Yr. Total335.2339.0346.3
Notes: 

Available seat-miles are a measure of the capacity of air passenger transportation. An available seat-mile is equal to one aircraft seat carried one mile.

Source: 

Bureau of Transportation Statistics, T-100 Segment

Load Factor on U.S. Airlines, Unadjusted (Tables 22-24)

Systemwide (Domestic + International) RPMs/ASMs (both unadjusted) in percent, Scheduled service only
2015201620172018
January79.180.279.478.8
February80.278.879.0
March83.983.683.5
April82.582.083.9
May84.183.884.0
June86.486.686.5
July87.486.886.6
August86.484.685.5
September83.083.381.7
October85.083.883.6
November82.483.183.8
December82.982.882.7
1 Mo. Value79.180.279.478.8
Yr. Value83.883.483.5
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment

Domestic RPMs/ASMs (both unadjusted) in percent, Scheduled service only
2015201620172018
January79.280.679.578.9
February82.480.880.9
March85.885.385.5
April84.984.185.2
May85.685.985.7
June87.487.687.2
July88.187.286.9
August86.684.785.4
September83.884.282.2
October86.485.485.7
November84.284.785.8
December84.083.483.5
1 Mo. Value79.280.679.578.9
Yr. Value85.084.684.6
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment

International RPMs/ASMs (both unadjusted) in percent, Scheduled service only
2015201620172018
January78.879.579.278.7
February75.373.974.3
March79.579.478.7
April77.177.380.8
May80.879.380.1
June84.484.584.9
July85.886.085.9
August86.084.385.8
September81.481.180.5
October81.680.178.7
November78.178.978.6
December80.381.280.8
1 Mo. Value78.879.579.278.7
Yr. Value81.080.781.0
Notes: 

Load factor is a measure of the use of aircraft capacity that compares Revenue Passenger-Miles (RPMs) as a proportion of Available Seat-Miles (ASMs).

Source: 

Bureau of Transportation Statistics, T-100 Segment