More than a dozen years after the Sept. 11 attacks, a last major piece of litigation against the airline industry and other defendants moved toward an end on Tuesday, as the Wall Street firm Cantor Fitzgerald revealed that it would settle its lawsuit for $135 million.

Cantor had accused American Airlines of negligence in allowing five terrorists to board the plane in Boston that crashed into the World Trade Center’s north tower, killing 658 of Cantor’s almost 1,000 employees in New York.

No amount of money, of course, could compensate Cantor or its families for the losses on Sept. 11, but the agreement, announced less than a month before the case was to be tried in Manhattan, followed years of legal sparring over what damages Cantor could seek.

After the proceeding, Cantor’s chairman, Howard W. Lutnick, said in a statement: “For the insurance companies, this was just another case, just another settlement, but not for us. We could never, and will never, consider it ordinary. For us, there is no way to describe this compromise with inapt words like ordinary, fair or reasonable. All we can say is that the legal formality of this matter is over.”