As National Transportation Safety Board officials comb the wreckage of the USAir jetliner that crashed Sunday at New York's LaGuardia Airport, hull and liability insurance underwriters in the United States, France and the United Kingdom are checking their wallets.

USAir Flight 405, a Dutch-made twin-engine Fokker F-28 carrying 47 passengers and four crewmembers, crashed during a freak spring snowstorm, burst into flames and skidded into the icy Flushing Bay at the end of the

runway, trapping many on board. Officials are still trying to determine whether the crash was caused by pilot error or weather conditions.John Hughes, spokesman for the Port Authority of New York & New Jersey, which runs LaGuardia Airport, said "at last count" on Monday morning, there were 26 confirmed dead and 25 survivors.

Lloyd's of London; Associated Aviation Underwriters of Short Hills, N.J.; La Reunion Aerienne and CAMAT Aviation, both of Paris, and Cigna of Philadelphia are among the underwriters contributing to USAir's $13 million in

hull coverage and $850 million in liability coverage, according to Scott Keller, a spokesman for the U.S. Department of Transportation.

Associated Aviation Underwriters, a U.S. underwriting pool run by Chubb & Sons of Warren, N.J., and by Continental Insurance Cos. of New York, supplies 30 percent of USAir's liability coverage, Mr. Keller said.

Lloyd's underwriters, which supply approximately 26 percent of USAir's liability coverage, were awaiting more information before they could comment on the New York City crash, according to Nick Doak, a Lloyd's spokesman.

USAir's insurance contract was only just renewed on Feb. 1, according to Catherine Aiello, a spokeswoman for Alexander & Alexander Inc., the airline's insurance broker.

The liability coverage includes bodily injury to those on the ground and property damage on the ground, as well as passenger bodily injury, said Mr. Keller of the Transportation Department.

"We try to assure that the carrier has coverage on file to ensure that it has the minimum insurance coverage limits," Mr. Keller said. "They've got lots of insurance."

That point may be debated, however, if the pilot is found to have been negligent.

Officials from the U.S. Department of Transportation and the Federal Aviation Authority declined to confirm whether the crash had been caused by pilot error, weather conditions or both.

USAir's reinsurance coverage was placed on the London market by A&A subsidiary Alexander Howden, according to Mr. Doak.

USAir Flight 405 had originated in Jacksonville, Fla., and was bound for Cleveland. It took off several hours late from New York, where the visibility was only three-quarters of a mile with a low ceiling of cloud cover.

According to Allen Morrison, port authority spokesman, the facility had been in "emergency snow mode" since Sunday afternoon, with extra runway workers and emergency services staff on hand.

Lynn McCloud, USAir spokeswoman, said Sunday the plane had been de-iced twice that night before taking off at LaGuardia.

This is not the first USAir crash to occur at the New York City-based airport. As recently as Sept. 20, 1989, a Charlotte, N.C.-bound USAir Boeing 737-400 trying to take off from LaGuardia skidded off the end of a runway and crashed into the East River, killing two people. Sixty-one people were rescued.