Officials say a man aboard a Lufthansa flight from Frankfurt to Belgrade was arrested on December 6 after threatening to open a plane door during the flight.
Lufthansa spokesman Andreas Bartels said the "passenger got up and tried to do something at the door, but was stopped by crew members and other passengers."
Bartels said it was not the cockpit door.
"The passenger was then restrained for the remainder of the flight in his seat and handed over to the authorities in Belgrade," he said.
Belgrade's Blic daily said the man is a Jordanian with an American passport.
Police questioned him after the plane landed in Belgrade.
Serbia's public prosecutor ordered the man into 48-hour pretrial detention on the grounds of endangering public safety.