European airport officials indicated severe delays were averted Friday because travelers, aware of reports that a hijacking might be attempted, checked in early and faced extra luggage searches calmly.

The Federal Aviation Administration warned U.S. airlines of a possible hijack by Palestinian terrorists in Europe this weekend. A London newspaper disclosed the warning Thursday, angering the American government, which feared its sources might be compromised.International Business Machines Corp., which employs 163,904 people outside the United States, advised them not to fly U.S. airlines on European and Middle Eastern routes until the end of April.

Police at Leonardo da Vinci Airport in Rome said the FAA warning prompted increased security and that more staff members were checking bags and working in the metal-detecting section.

No takeoff delays were reported, and reservations agents at U.S. airline counters said the number of cancellations was not unusual.

Security experts in Italy also were wary because of the approaching anniversary of the U.S. bombing of Libya on April 15, 1986.

On April 14 last year, a bomb exploded at a USO in Naples, killing an American woman and four other people. The Japanese Red Army was blamed.

ANSA, the Italian news agency, quoted Libyan Ambassador Abdulrahman Shalgam as telling reporters Friday that allegations of Libyan involvement in attacks allegedly planned were an "absurdity."

At London's Heathrow airport, passengers found themselves in long lines as bags were carefully searched and their owners questioned.

Some passengers traveling on American lines faced double checks, by the airport staff and the airlines. Airlines tightened security after the bombing Dec. 21 of Pan Am Flight 103, in which 270 people were killed.

Most travelers appeared to have arrived early, as suggested, and delays generally were limited to a little more than an hour.

"I think most people have been well informed and are taking advice about arriving early and not carrying electrical equipment," said Bob Hearn, manager of customer services at British Airways Terminal 4.