Sounds like TWA flight 800

There seems to be a pattern. Whenever a suspicious event happens, a blackout, refinery explosion or even a missile being fired at a plane, the first thing the FBI says is "It's not a terror incident". As if the pilot mistook a missile for a bottle rocket. Cripes! He was out over the ocean. That's some bottle rocket or flare.

FBI agents and Homeland Security officials spent the weekend investigating the report of a possible missile fired at an American Airlines plane taking off from Los Angeles International Airport.
Sources tell ABC News the pilot of American Airlines Flight 621, en route to Chicago, radioed air traffic controllers after takeoff from LAX. He told them a missile had been fired at the aircraft and missed.

The plane was over water when the pilot said he saw a smoke trail pass by the cockpit.

FBI agents believe it was a flare or a bottle rocket, but say they may never know if that's what it actually was. link