President Reagan has approved, as expected, a Civil Aeronautics Board decision to suspend immediately the operating authority of LOT, the Polish national airline.

The board's action had followed notification by the State Department that the Polish government had been informed that the United States wanted to suspend Polish-American civil aviation relations because of the continuing imposition of martial law in Poland.

Before the current crisis and subsequent suspension, LOT had been operating six round trips a week between New York and Warsaw, the CAB said.

Responding to a similar State Department request citing the Soviet Union's involvement in the Polish situation, the board also has moved to withdraw the U.S. operating privileges of Aeroflot, the Soviet Union's national airline.

Aeroflot was given until 9 a.m. Monday to explain why its privileges to fly to and from the United States shouldn't be withdrawn. The board said it intends to finalize the withdrawal of privileges not later than Tuesday.

Aeroflot currently operates two round trips a week between Moscow and Washington's Dulles International Airport. Aeroflot had ended its New York-Moscow service when unions at Kennedy International Airport refused to service Aeroflot after the Soviet Union sent troops into Afghanistan.

Pan American World Airways ended its service to Warsaw and Moscow several years ago in a move to drop unprofitable routes.