New York financier Carl C. Icahn disclosed yesterday that he controls a 20.5 percent stake in Trans World Airlines Inc. and is evaluating whether to seek control of the airline.

Icahn and other executives of his New York investment firm were not in their office yesterday and were unavailable for comment.

TWA President and Chief Executive Officer C. E. Meyer Jr. said "Mr. Icahn's presence is uninvited and undesirable. . . . Consequently, we intend to take all appropriate steps to protect the company from any actions that are inconsistent with our goals."

In a filing with the Securities and Exchange Commission, Icahn and a group of companies he controls said they were evaluating their alternatives, including seeking control of the carrier.

Icahn's group also said it "may explore the possibility of ACF Industries Inc. making a proposal for a merger or business combination" with TWA, the news service said. Icahn is chairman of ACF Industries, a transportation-leasing concern.

The SEC filing said the Icahn group holds 6.745 million of TWA's 33 million total common shares outstanding, including purchases of 5.15 million shares bought between March 21 and May 8 at prices ranging from $12.625 a share to $16 a share.