The missing pieces of the long-distance travel picture include trips by personal vehicles, general aviation, and cruise ships. Vehiclemiles of travel on rural interstate highways are occasionally used as a surrogate for long-distance highway travel, but there is no methodology for separating local from longdistance travels within rural areas. Takeoffs and landings of general aviation aircraft are not a good indicator because many flights take off and land at the same airport rather than carry people to distant destinations. Numbers of passengers boarding and debarking from cruise ships in each port are measured, but the passenger lists have not been compiled into trips since June 2012.