Senators on the Pan Am Flight 103 commission announced legislation yesterday to appoint security managers at high-risk airports and to require a system for notifying passengers of terrorist threats.

"It's essential that we proceed," said Sen. Frank R. Lautenberg (D-N.J.), a member of the now-defunct presidential commission. "The terrorists are not giving up, and we can't either."

"It can no longer be business as usual with the FAA {Federal Aviation Administration} and the airlines," Lautenberg said.

Lautenberg and two fellow commission members, Sen. Alfonse M. D'Amato (R-N.Y.) and Rep. James L. Oberstar (D-Minn.), said they expected strong bipartisan support for the bill.

The Senate bill, to be matched by a similar House measure next week, would give special FAA managers responsibility for security at airports where terrorists are considered likely to operate.

It also would require the FAA and the FBI to assess the security threat to domestic airports and set up security screening of mail and cargo.

The bill would prohibit selective notification of government employees when there is a threat and would order that guidelines be set up for notifying the public when there is a credible threat against a flight.

The December 1988 bombing over Lockerbie, Scotland, blamed on unidentified terrorists, killed all 259 people aboard the London-New York flight and 11 people on the ground.