Government reluctance to make public an air terrorism threat in Europe is bringing new calls from relatives of the Pan Am Flight 103 bombing victims for disclosure of all serious threats against commercial aviation.

Several relatives of victims of the Dec. 21 bombing of Pan Am Flight 103 said they believe the way the government handles terrorism bulletins warns diplomatic and military personnel while keeping other potential passengers uninformed about risks.British investigators have concluded that a terrorist bomb concealed in a radio-cassette player blew up the Boeing 747 over Scotland, killing all 259 people aboard and 11 others on the ground in Lockerbie, Scotland.

The relatives, in telephone interviews, criticized government failure to provide the public with information about terrorist warnings, such as the March 16 memorandum sent by the Federal Aviation Administration to airlines, airports and European security officials.

Relatives of the Lockerbie victims say the lack of public notification puts travelers at unnecessary risk. "We don't think they should use the American public as live bait," said Colleen Hermann, of Huntington, N.Y., whose brother John Michael Ahern was killed on Flight 103.

Bert Ammerman, a spokesman for the relatives of Lockerbie victims, said the group is not calling for general public announcements every time there is a terrorist threat. But he said that until prudent security measures can be taken to protect American carriers throughout the world, a telephone number should be set up for travellers to call to get information on any threat against a flight they plan to take.

"I don't think that's going to paralyze the aviation industry," said Ammerman, of Demarest, N.J., whose brother, Tom, was killed in the Pan Am bombing.

Some of the relatives noted that Pan Am warned passengers of a New York-Paris flight last week of a bomb threat and gave them the option of taking another plane. Pan Am said only 17 of the 200 passengers left the plane, and 11 of those flew the same flight the following day.

Paul Hudson, an Albany, N.Y., lawyer who lost his 16-year-old daughter Melina in the Pan Am explosion, said present security policies amount to a selective warning system.

"What happens when this information is kept secret and yet is passed around to literally thousands of security people is that it is bound to leak out and hurt the credibility of security," Hudson said. "It then tends to sow panic even among those not directly threatened."

Tim Cole, a Washington aviation consultant, said if all threats were made public, they might become so commonplace that people would simply ignore them. "With 600 or so threats a year, you'd be crying wolf all the time," he said.

Officials say all but a handful of threats are hoaxes.