Southwest Is the Busiest U.S. Airline

The Department of Transportation (DOT) on Thursday released data for the first five months of 2008, showing the busiest U.S. airlines and airports for the period.

A few highlights:

Total Traffic

The number of people flying on U.S. carriers between January and May 2008 increased 0.1 percent, to 310.4 million, over the same period last year.

Load Factor

The airlines’ collective load factor (the percentage of seats occupied) held steady at 78.4 percent.

Busiest Airports

For domestic flights, Atlanta boarded the most passengers during the period; Chicago O’Hare and Dallas/Ft. Worth were second and third. For international, it was Miami, followed by New York (JFK) and Atlanta.

And overall, the ten busiest U.S. airports were Atlanta, Chicago O’Hare, Dallas/Ft. Worth, Denver, Los Angeles, Las Vegas, Phoenix, Houston, Orlando, and Detroit.

Busiest Airlines

The DOT measures “enplanements,” or passenger boardings. By that measure, the U.S. airlines with the most domestic passengers were [% 2638576 | | Southwest %], American, and Delta. Internationally, the top carriers were American, Continental, and United.

When domestic and international are combined, the ten busiest airlines were Southwest, American, Delta, United, US Airways, Northwest, Continental, AirTran, JetBlue, and SkyWest.

There are other important metrics for measuring the relative sizes of airlines, including revenue and revenue-passenger-miles, according to which Southwest still falls short of the top spot.

Enplanements, however, are an especially meaningful gauge since they reflect the number of times an airline delivers the service it is in business to deliver, in this case flying a passenger from point A to point B.

Serving 42.8 million travelers during the five months covered by the DOT report, Southwest will probably retain bragging rights as the busiest airline until the [% 2550074 | | Delta-Northwest merger %] takes effect. While there’s no DOT data to support it, Southwest could also make a strong claim to being the country’s most popular airline. So at least for now, the busiest and the most popular carrier are one and the same.