Officials say the black boxes of a Boeing jetliner that crashed in South Korea last month stopped recording about four minutes before the accident.

The deadliest accident in aviation history occurred in 1977, when two Boeing 747 jumbo jets collided on a foggy runway on the Spanish island of Tenerife, killing 583 of the 644 people on board the planes. Spanish investigators blamed the captain of the KLM 747 for taking off without clearance from air traffic controllers.