American Airlines reported its passenger traffic dropped by more than 13% in February. American reported it filled about 74 percent of its seats.
Southwest Airlines reported its passenger traffic dropped 6 percent in February.
The Dallas-based carrier reported 69 percent of its seats were filled.
The U.S. airline industry has been fighting falling revenue since rising fuel bills pushed carriers into the red last year. Soft business travel is also a major reason concern.
US Airways reported traffic down 9% with Alaska Airlines saying its traffic dropped 10%.
Among smaller regional airlines, American Eagle reported a 14 percent drop in traffic.