NEW YORK (CNN/Money) - Airline traffic is tumbling as the war in Iraq and concerns about the Asian virus SARS are keeping travelers out of the air.

Major U.S. carriers are reporting steep declines in March traffic, particularly on international routes. The later Easter holiday, which comes in April this year rather than March, as it did last year, also is affecting year-to-year traffic comparisons.

Continental CEO says that the airline may suspend flights to Hong Kong because up to 30 percent of passengers aren't showing up due to concerns about SARS.

Delta Air Lines, the nation's No. 3 airline, reported Thursday that its overall traffic was off 8.1 percent, outstripping the 3 percent cut in capacity the airline made to try to respond to the drop in demand. Domestic travel on mainline Delta Air Lines was 7.3 percent, while its international traffic fell by 20 percent, with Latin American traffic falling by about 9 percent while trans-Atlantic and trans-Pacific business fell by better than 21 percent.

Southwest Airlines, the one major carrier that has seen profits and traffic growth since the Sept. 11 terrorist attacks, reported Thursday that the start of fighting in Iraq last month affected its March traffic, and that April bookings also are being affected.

"Prior to the war, bookings for April travel were good. Since the war began, booking trends have been inconsistent," Southwest CEO James Parker said. "Uncertainties created by the war with Iraq render it impossible to predict future bookings and traffic."

Related stories SARS could cause world recession Asian virus keeping fliers home War dents business travel

Southwest, which doesn't have any international flights, managed to post a 1.1 percent increase in March traffic, but that's down from its gains in the previous two months. For the first quarter, Southwest traffic is up 4.8 percent.

American Airlines, the world's largest carrier which has been teetering on the edge of a possible bankruptcy filing, saw miles flown by paying passengers fall 4.8 percent in March, with domestic travel off 5.1 percent. Travel across the Atlantic fell 8.5 percent while trans-Pacific traffic actually rose 10.9 percent, although that made up just 2.4 percent of American's overall traffic.

Continental Airlines, the nation's No. 5 carrier, saw traffic sink 8.3 percent overall, with domestic traffic down 7.6 percent and international traffic off 9.3 percent. That came from a 5.5 percent reduction in trans-Atlantic traffic and a 21.9 percent tumble in trans-Pacific traffic.

Continental CEO Gordon Bethune told CNNfn Wednesday that the airline is considering suspending its Newark, N.J., to Hong Kong flights because passengers fear the Severe Acute Respiratory Syndrome (SARS) disease. Of 2,223 cases of SARS confirmed by the World Health Organization, 1,898 occurred in mainland China and Hong Kong.

"Bookings are OK, but sometimes as many as 30 percent of the customers don't show up," Bethune told CNNfn. Continental now has five round-trip flights a week between its Newark hub and Hong Kong.

Air Canada, which has yet to report March traffic, blamed concerns about SARS and the war in Iraq for a sharp drop in business that prompted it to file for bankruptcy Tuesday.