The airlines also set all-time annual highs for systemwide, domestic and international revenue passenger miles (RPMs) and available seat-miles (ASMs).

Annual systemwide load factor – the measure of the use of airline capacity – was up slightly from 2016. Domestic load factor was unchanged while international load factor rose because passenger travel growth outpaced capacity expansion (Tables A, B, C). Load factor remained below peak levels of previous years (Tables A, B, C).

Annual Trends:           

Passengers

• Systemwide passenger enplanements (849.3 million) reached an all-time annual high, up 3.1 percent from the previous high (824.0 million) reached in 2016 (Table A).
• Domestic passenger enplanements (741.6 million) reached an all-time annual high, up 3.0 percent from the previous high (720.0 million) reached in 2016 (Table B).
• International passenger enplanements (107.7 million) reached an all-time annual high, up 3.5 percent from the previous high (104.0 million) reached in 2016 (Table C).

Revenue Passenger-Miles

• Systemwide RPMs (964.3 billion) reached an all-time annual high, up 3.3 percent from the previous high (933.5 billion) reached in 2016 (Table A).
• Domestic RPMs (683.7 billion) reached an all-time annual high, up 3.6 percent from the previous high (660.0 billion) reached in 2016 (Table B).
• International RPMs (280.6 billion) reached an all-time annual high, up 2.6 percent from the previous high (273.5 billion) reached in 2016 (Table C).

Available Seat-Miles

• Systemwide ASMs (1.15 trillion) reached an all-time annual high, up 3.2 percent from the previous high (1.12 trillion) reached in 2016 (Table A).
• Domestic ASMs (808.3 billion) reached an all-time annual high, up 3.6 percent from the previous high (780.1 billion) reached in 2016 (Table B).
• International ASMs (346.5 billion) reached an all-time annual high, up 2.2 percent from the previous high (338.9 billion) reached in 2016 (Table C).

Load Factor

• Systemwide load factor (83.5) was up 0.1 point from 2016 (83.4) but down 0.3 points from the all-time annual high (83.8) reached in 2015 (Table A).
• Domestic load factor (84.6) was unchanged from 2016 but down 0.4 points from the all-time annual high (85.0) reached in 2015 (Table B).
• International load factor (81.0) was up 0.3 points from 2016 (80.7) but down 1.3 points from the all-time annual high (82.3) reached in 2013 (Table C).

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 in ASMs.

December Air Traffic

U.S. airlines’ December systemwide (domestic and international) scheduled service passenger enplanements rose 0.1 percent from November, rising to 72.3 million to reach a new all-time seasonally-adjusted high, rising for the third consecutive month (Table 1).

From November 2017 to December 2017 enplanements on domestic flights increased 0.1 percent while enplanements on international flights to and from the U.S. rose 0.1 percent resulting in a 0.1 systemwide increase (Tables 1, 2, 3).

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

Trends (Percent changes based on unrounded numbers)

Seasonally-adjusted

The following seasonally-adjusted measures of U.S. airlines’ December air traffic reached all-time highs:

• Systemwide passenger enplanements (72.3 million) reached a new seasonally-adjusted all-time high, up 0.1 percent from the previous high in November 2017 (72.2 million) (Table 1).
• Domestic passenger enplanements (63.22 million) reached a new seasonally-adjusted all-time high, up 0.1 percent from the previous high in November 2017 (63.17 million) (Table 2).
• Systemwide available seat-miles (ASMs) (97.7 billion) reached a new seasonally-adjusted all-time high, up 0.2 percent from the previous high in October 2017 (97.4 billion) (Table 7).
• Domestic ASMs (68.5 billion) reached a new seasonally-adjusted all-time high, up 0.3 percent from the previous high in August 2017 (68.3 billion) (Table 8).

The following seasonally-adjusted measures of U.S. airlines’ December air traffic declined from all-time highs:

• International passenger enplanements (9.05 million) were down 0.7 percent from the all-time seasonally-adjusted high (9.11 million) reached in April 2017 (Table 3).
• Systemwide revenue passenger miles (RPMs) (81.6 billion) were down 0.3 percent from the all-time seasonally-adjusted high (81.8 billion) reached in November 2017 (Table 4).
• Domestic RPMs (58.1 billion) were down 0.2 percent from the all-time seasonally-adjusted high (58.2 billion) reached in November 2017 (Table 5).
• International RPMs (23.5 billion) were down 1.2 percent from the all-time seasonally-adjusted high (23.8 billion) reached in April 2017 (Table 6).
• International ASMs (29.1 billion) were down 0.3 percent from the all-time seasonally-adjusted high (29.2 billion) reached in October 2017 (Table 9).

Systemwide load factor (83.5) was down 1.3 points from the all-time seasonally-adjusted high (84.8) reached in October 2015 (Table 10). Domestic load factor (84.8) was down 1.1 points from the all-time seasonally-adjusted high (85.9) 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).

The seasonally-adjusted load factor fell from November (84.2) to December (83.5) as a result of a 0.3 percent decline in RPMs from November to December combined with a 0.5 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

The following unadjusted measures of U.S. airlines’ December air traffic reached highs for the month of December:

• Systemwide passenger enplanements (70.2 million) reached an all-time December high, up 3.2 percent from the previous high (68.0 million) reached in 2016 (Table 13).
• Domestic passenger enplanements (61.2 million) reached an all-time December high, up 3.5 percent from the previous high (59.2 million) reached in 2016 (Table 14).
• International passenger enplanements (9.0 million) reached an all-time December high, up 1.7 percent from the previous high (8.8 million) reached in 2016 (Table 15).
• Systemwide RPMs (79.6 billion) reached an all-time December high, up 3.4 percent from the previous high (77.0 billion) reached in 2016 (Table 16).
• Domestic RPMs (56.9 billion) reached an all-time December high, up 3.9 percent from the previous high (54.8 billion) reached in 2016 (Table 17).
• International RPMs (22.7 billion) reached an all-time December high, up 2.3 percent from the previous high (22.2 billion) reached in 2016 (Table 18).
• Systemwide ASMs (96.2 billion) reached an all-time December high, up 3.5 percent from the previous high (93.0 billion) reached in 2016(Table 19).
• Domestic ASMs (68.2 billion) reached an all-time December high, up 3.8 percent from the previous high (65.7 billion) reached in 2016 (Table 20).
• International ASMs (28.0 billion) reached an all-time December high, up 2.8 percent from the previous high (27.3 billion) reached in 2016 (Table 21).

Systemwide load factor (82.7) was down 1.7 points from the all-time December high (84.4) reached in 2013 (Table 22). Domestic load factor (83.5) was down 1.6 points from the all-time December high (85.1) reached in 2013 (Table 23). International load factor (80.8) was down 2.1 points from the all-time December high (82.9) reached in 2013 (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 77 carriers as of March 6 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 December, 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 December and international numbers through September 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 December, U.S. carriers reported 41,877 foreign point-to-point passengers. For January through December, U.S. carriers reported 634,555 foreign point-to-point passengers.

Data are subject to revision. BTS has scheduled April 12 for the release of January traffic data. None of the data are from samples so measures of statistical significance do not apply.

Annual Tables

Monthly Seasonally-Adjusted Tables

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

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

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

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

Monthly Unadjusted Tables

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

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

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

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