A British Airways TriStar jet carrying 343 people narrowly avoided another aircraft over the coast of southern England, a spokesman for the airline said. News reports said passengers quoted crew members as saying the planes missed each other by just five feet. The British Airways plane, which was flying from Paris to London's Heathrow Airport, had to swerve sharply when the pilot spotted the other plane 300 yards away on a collision course, the spokesman said. Both planes were flying at a height of 18,000 feet. The spokesman refused to identify the other plane, but news reports said it was a Bulgarian Balkan Air Tupolev 154 jet, carrying more than 200 passengers from Sofia heading for Gatwick Airport.