For the third straight year, Southwest Airlines Co. carried more passengers than any other U.S. carrier, while American Airlines Inc. carried the most international passengers, the government said Monday.
The U.S. Bureau of Transportation Statistics, which released its annual traffic summary for airlines and airports Monday, also said Atlanta Hartsfield remains the nation's busiest airport by a comfortable margin over No. 2 Chicago O'Hare.
Dallas/Fort Worth International Airport remained fourth behind Los Angeles International Airport.
Overall, the bureau said, passenger traffic in 2009 dropped 5.3 percent from 2008 and was 8.2 percent below 2007. International traffic declined 5.8 percent last year from 2008 as the U.S. industry suffered from a drop in demand.
Southwest, with 101.3 million passengers, led U.S. carriers in total passengers, followed by American with 85.7 million and Delta Air Lines Inc. with 67.7 million.
Delta usually leads the list of airlines ranked by passenger traffic, but two factors skewed the statistics in favor of Southwest for total passengers and American for international passengers.
One, the industry most often uses "revenue passenger miles" - passengers multiplied by the number of miles they traveled - to rank carriers by traffic.
However, the Bureau of Transportation Statistics looks at the number of passengers who boarded airplanes without regard for whether they were traveling 240 miles from Dallas to Houston or 7,300 miles from New York to Delhi, India.
And under that measure, Dallas-based Southwest, which has no international flights and has concentrated on shorter flights, led the nation by a wide gap.
Second, before Jan. 1, the bureau counted Delta and its October 2008 merger partner, Northwest Airlines Inc., as two separate airlines.
Had Delta's and Northwest's numbers been combined, it would have been ranked at the top for both total passengers and international passengers.
Including Northwest, Delta had 108.6 million total passengers in 2009, beating Southwest's 101.4 million.
Delta carried 12.1 million international passengers last year, behind Fort Worth-based American's 19.6 million. But including Northwest's international travelers, Delta totaled 20.5 million.
Next were Continental Airlines Inc. with 12 million, United Airlines Inc. with 10.5 million and US Airways with 6.5 million.
Atlanta Hartsfield-Jackson International Airport remained at its accustomed top spot, even though its passenger totals declined from 2008. Hartsfield boarded 42.1 million passengers, the bureau said, down 3.4 percent from 43.6 million in 2008.
No. 2 O'Hare, with 31.1 million passengers, saw the biggest decline from 2008, 2.5 million, or 7.5 percent.
D/FW Airport's boardings dropped 1.9 percent, down from 27.1 million in 2008 to 26.6 million in 2009.
Only San Francisco, the 10th-busiest airport, saw an increase in passenger traffic, the agency said.
Total passengers boarded in 2009, in millions Airline Passengers 1. Southwest 101.3 2. American 85.7 3. Delta 67.7 4. United 56 5. US Airways 51 Total international passengers boarded, in millions Airline Passengers 1. American 19.6 2. Delta 12.1 3. Continental 12 4. United 10.5 5. Northwest 8.3
SOURCE: U.S. Bureau of Transportation Statistics