The director of the Smithsonian's National Air and Space Museum resigned yesterday, citing continuing controversy over his role in the canceled Enola Gay exhibit.

Martin O. Harwit said he was ending his eight-year tenure as director of the world's most visited museum "to satisfy the Museum's critics and allow it to move forward." His announcement came three months after a demand from 81 members of Congress that he resign.

That pressure, along with protests by veterans and other critics, led the Smithsonian Institution to cancel the planned exhibit on the decision to drop the atomic bomb on Japan. Yesterday, amid continuing calls for congressional hearings and changes at the Air and Space Museum, Harwit, 64, wrote Smithsonian Secretary I. Michael Heyman: "There is no choice but to resign: The Museum's welfare and future are too important."