A British Airways jumbo jet carrying 169 passengers and 16 crew members came within 600 feet of colliding with a small private plane while approaching Dulles International Airport Wednesday.

Federal Aviation Administration spokesman Fred Farrar said yesterday the pilot of the plane, bound for Washington from London, had been advised by the airport control center of the small plane's whereabouts and did not need to take evasive action. An FAA investigation of the incident is planned, he said.

Farrar said FAA officials have no clues as to the idenity of the pilot of the small plane, which had apparently filed no flight plan. "It was definitely not under our control, or we'd know who it was," Farrar said.

According to an account filed by Britain Airways pilot, Olive Morris, the 747 was about 15 miles south of Dulles shortly after 3 p.m. in clear weather when it was advised that another plane was in its path. Morris said he was flying at 4,900 feet when he spotted the small twin engine plane flying 100 feet below and 600 feet to the right of his aircraft.

The small plane veered sharply, Morris' said, and the British Airways plane landed without incident.

A spokesman for British Airways said yesterday the near-collision posed no danger to the occupants of the jet, and that none of the passengers had registered complaints about the incident.