Two Russian-speaking men were arrested at Tegel airport in Berlin, Germany, after a witness overheard a "suspicious conversation" between them suggesting that a flight might be hijacked, police told CNN.
The incident happened at check-in for an Air Berlin flight in terminal C of the airport, where a woman overheard the two men speaking in Russian, leaving the impression that the flight was going to be hijacked, police said.
The woman notified authorities, and the men, 49 and 26, were taken into custody. They are to be questioned by state authorities.
All other passengers were also taken off the plane and questioned.
Police will not yet say where the suspects are from.
The flight was to head to Moscow, Russia, but the plane is grounded and being searched by German investigators.
The other passengers were able to depart on a different plane after several hours' delay, authorities said.