Korean Air 747 mistakenly flagged as hijacked after 9/11 attacks

On 11 September 2001, four aircraft were hijacked in the United States. Two were flown into the World Trade Center, one into the Pentagon, and one crashed in Pennsylvania. North American airspace was closed.

Hours later, authorities feared a fifth aircraft might also have been seized. It was a Korean Air Boeing 747-400, registered HL7404, operating flight KE085 from Seoul-Incheon to New York-JFK with 215 passengers on board, and a refuelling stop at Anchorage had been scheduled.

The crew was in contact with Korean Air through the ACARS messaging system when they used the three-letter code HJK, which stands for hijacking. According to the report, the crew likely intended to tell the airline's headquarters about the attacks in the United States. In Korea, however, a different suspicion arose: that the pilots might be signalling that their own 747 had been hijacked.

The information was passed from Korea to US authorities. Coming after four actual hijackings the same day, the signal could not be dismissed, and the aircraft came close to being shot down. In the end, nothing was wrong on board.