America's two leading commercial aircraft makers charge they were threatened with loss of future sales if they pursued complaints of unfair trade by Airbus Industrie, a European government-financed consortium that is building competing planes.

The charges of coercion, given in congressional testimony Tuesday, sparked a request yesterday by Reps. James J. Florio (D-N.J.) and Howard C. Nielson (R-Utah) for a government investigation to determine if the threats cost U.S. sales and violate international trade rules.

The Senate Thursday night approved an amendment to its massive trade bill aimed at the government subsidies to the Airbus consortium. The provision was sponsored by Sens. Brock Adams (D-Wash.) and John C. Danforth (R-Mo.), where Boeing Co. and McDonnell Douglas Corp. are headquartered.

McDonnell Douglas urged a go-slow position in February when the Reagan administration was considering the possibility of trade sanctions against Airbus for its heavy government subsidies and its use of official government pressure to sell planes. The McDonnell Douglas stance angered U.S. trade officials and congressmen who had been pressing for action at the company's request.

Reports circulated at the time that McDonnell Douglas acted under pressure from European customers, including national airlines controlled by the same governments that are part of the Airbus consortium: France, Britain, West Germany and Spain.

James E. Worsham, a vice president of McDonnell Douglas, confirmed the pressure under questioning by Florio at the House Commerce subcommittee hearing Tuesday.

"There have been some comments," he said, "that it would be difficult for some of the international airlines to select McDonnell Douglas' product with us having a very, very high profile at that immediate time."

O.M. (Rusty) Roetman, a Boeing vice president, acknowledged that his company also felt pressure from customers not to push unfair trade cases against Airbus. Florio asked if the threats included either the "denial of future contracts . . . or cancellation of existing contracts.

"There has been pressure from certain of our customers, who have asked us not to take too high a profile, to let this thing run its course," Roetman replied. "We don't believe it is in our best interests to {take a low profile} over an extended period of time."

Nonetheless, he added that further involvement by Boeing in an unfair trade complaint against Airbus could make it, "in some markets, very difficult to continue to sell at the volume we have been selling."

Ranking administration trade officials said the dispute with Western European nations over their heavy government funding is growing into "an enormous controversy" that "is going to be very nasty."

The officials said it involves huge sums of money, one of the few American industries that remains an export leader, and the Europeans' determination to become a factor in the commercial aircraft business, no matter what it costs their governments.

"In the next few weeks, the government will have to decide how much of a hassle this will be," the official said. He added that the Cabinet-level Economic Planning Council will be meeting on the issue soon.

Administration trade officials and the domestic aircraft industry complain that the governments of Britain, France, West Germany and Spain have supported Airbus with $8 billion in subsidies for almost 20 years and the consortium has never made a profit.

"As an economic rule, subsidized production and competition unfairly {puts at a disadvantage} companies attempting to compete on purely commercial terms and creates uneconomic excess capacity at great expense to taxpayers," Deputy U.S. Trade Representative Michael B. Smith told the Florio subcommittee.

"It is in trade terms just as protectionist and distorting as other, more classic protectionist measures."

Administration sources said they have information that the governments supporting Airbus have directly intervened with foreign airlines, often using landing rights or aid as bait to get international airlines to buy their planes instead of Boeing or McDonnell Douglas products.