LONDON (AP) _ Fire broke out today in a fast-food restaurant at London's Heathrow, delaying hundreds of flights at the world's busiest international airport and snarling air traffic across Europe. No injuries were reported.

The fire started before dawn in a ventilation shaft above a deep-fat fryer at a Burger King in Terminal 1 and quickly spread through the air ducts.

Flames leapt through the terminal roof for two hours. Firefighters labored for 3 1/2 hours before bringing it control, extinguishing it two hours later.

``The whole sky above the terminal seemed to be glowing,'' said Bob James, an American oil engineer who landed at Terminal 3 soon after the fire broke out. ``All you could see was smoke and flames.''

The blaze temporarily shut down three of the airport's four terminals, causing delays for more than 50,000 airline passengers and traffic jams on roads leading to the airport, 15 miles west of central London.

Some motorists abandoned cars alongside the M4, the main highway leading to Heathrow, and tried walking to the terminal carrying their luggage. Police warned that abandoned cars would be towed.

Terminal 1, which handles mainly domestic flights and flights to Europe, reopened for landings after about nine hours and for outgoing flights an hour later.

Flights into the terminal had been diverted to other airports in southeast England.

Terminals 2 and 3 reopened after about two hours.

Terminal 4, which handles mostly British Airways overseas flights and is about three miles from the three other terminals, was the only one unaffected.

Officials said there would be delays and changes to flight schedules throughout the day.

British Airways canceled all its British and international flights from Terminal 1 until the afternoon.

``Typically on a Friday the airport will handle about 170,000 passengers. Just about half of those will be into and out of Terminal 1,'' said Roger Cato, Heathrow's managing director.

The restaurant was closed at the time the fire started.

``There were very few people around and when the smoke detector started everyone thought it was a false alarm,'' said British passenger Marianne Billington, 57. ``It took about half an hour for people to start taking it seriously.''

British Broadcasting Corp. reported that at one point cars were backed up for five miles along the M4. Traffic also backed up on the M25, the highway that circles greater London and is linked to the M4.

Last year, 57 million people used Heathrow _ more international passengers than any other airport in the world.