Washington ? The largest U.S. airlines will ask Congress to suspend $9 billion in annual taxes and extend war-risk insurance to alleviate the potentially crippling impact of a war in Iraq, outlined in a report released Tuesday by the Air Transport Assn.

If the worst happens — a major terrorist attack occurring when war breaks out — the largest airlines could collapse, the industry association said.

The most likely scenario is a war in which passenger traffic falls more sharply than in the 1991 Gulf conflict, according to the report. In that case, airlines would lose $10.7 billion, nearly 10 percent of daily flights would be canceled and 70,000 airline jobs would be cut.

“We’re in a crisis,” said James May, the association’s president. He said the airlines weren’t asking for a bailout, but for help in withstanding the consequences of war.

A relatively short conflict like the first Gulf War would cause $7.6 billion in losses, the report said.

The report’s scenarios were based on recent bookings, data from the last war and assumptions about the economy and passenger behavior.

The government’s decision to raise the nation’s terror alert status to orange last month produced a 20 percent decline in advance bookings despite fares that are at 15-year lows, according to the association, which represents the largest air carriers. The alert has since been lowered to yellow.

The airlines want a holiday from six taxes they pay into a trust fund, beginning with the start of the war and ending one year after it ends. They also want the government to pay for security improvements, on grounds they are a matter of national defense.

Congress stepped in after the Sept. 11 attacks, granting airlines $5 billion in cash and $10 billion in loan guarantees to offset losses from four days of groundings and passengers’ reluctance to fly. The Federal Aviation Administration also issued war risk insurance — which the airlines want extended — after private insurance became too expensive.