The Senate today may consider an agreement to set a $320,000 limit on the amount that airlines on international flights would have to pay the estates of American crash victims under a sort of international no-fault insurance.

The ceiling for non-Americans would be $120,000. American passengers would help to make up the difference through a $2-a-ticket surcharge on international flights.

The issue, long debated, has the unusual feature of being favored by the American Bar Association and opposed by the Association of Trial Lawyers of America (ATLA).

The disputed document is known as the Montreal Protocols. It was negotiated eight years ago, but remains unratified despite the support of the Ford, Carter and Reagan administrations and the Senate Foreign Relations Committee. Passage requires a two-thirds' vote of the Senate, and the vote is expected to be close.

The protocols are part of an American effort to increase international aviation liability limits, presently $75,000 per individual, and to modernize international cargo and ticketing agreements. Under the existing treaty, known as the Warsaw Convention, the liability limits can be exceeded if willful misconduct by an airline is proven.

The new proposal would delete the willful-misconduct clause and would limit airline liability to $120,000 per individual. But for U.S. passengers an additional $200,000 would be available, paid from a fund financed by a $2-a-ticket surcharge.

There is also an inducement in the pact for airlines to settle within six months, something that rarely happens in aviation litigation today.

The treaty would not apply to domestic accidents but would apply, for example, to the Washington-New York leg of a Washington-New York-London ticket. It would also not affect the liability of airplane manufacturers, who have shared liability payoffs in some recent crashes.

While substantially more than $320,000 has been paid to the estates of some air crash victims, treaty advocates say statistics show that 85 percent of the cases involving Americans are settled for less.

A significant issue, however, is one of aviation safety. The handful of attorneys who specialize in aviation liability law have used the post-crash discovery system to make major contributions in accident investigation.

Lee Kreindler, a New York attorney who found several important documents while representing plaintiffs in the world's worst single-plane crash (a 1974 accident outside Paris that killed 364), said yesterday:

"There is no excuse in 1983 for any limitation of damages for anyone, certainly not airlines. Airlines are mature businesses, and should be responsible for the damages they cause just as doctors, lawyers and Indian chiefs are."

But Franklin Willis, a deputy assistant transportation secretary, said that the proposal "avoids the need for a very expensive specialty aviation trial attorney who can examine all the government reports, then decide the best way to present them to a jury. That system works wonders for the well-to-do who are looking for high settlements and who can afford paying the contingency fee and to wait the two to five years" that it sometimes takes to settle cases.

Craig Baab, of the American Bar Association, said the advantage of quick settlement and the fact that the liability ceiling is the best the United States could negotiate are sufficient reasons to support the proposed treaty. Most other countries have substantially lower liability limits, he noted, which is why the supplemental fund was set up for U.S. citizens.