An easyJet flight made an unplanned landing and its passengers were evacuated down emergency chutes after the pilot learned of a "suspicious conversation".
The London-bound flight from Ljubljana, in Slovenia, was forced to divert to Cologne-Bonn airport, in Germany, at around 5.30pm on Saturday.
All 151 passengers were made to leave the plane and undergo a security check.
A spokesman for Cologne-Bonn airport said: "A plane on the way from Ljubljana to London has landed this evening around 6.30pm in Cologne unplanned.
"Prior to this, the pilot had been informed about a suspicious conversation on board, after which he decided to make an unscheduled landing in Cologne/Bonn.
"After the safe landing of the aircraft of the type A319, the 151 passengers left the machine via emergency slides and were taken to a transit gate.
"The police have been informed and have taken action.
"Thus, passengers had to undergo a check immediately after landing."
German media reported police destroyed some unclaimed baggage.
Flights were suspended at the airport for three hours.
An easyJet spokeswoman said: "easyJet can confirm that flight EZY3246 from Ljubljana to London Stansted diverted to Cologne today.
"The captain took the decision as a precaution to enable the aircraft to go through additional security checks in Cologne where the aircraft was met by the police.
"In compliance with the local authorities' guidance, passengers disembarked to allow additional security checks to be performed."
She added the passengers had been given a hotel stay for the night and would fly back on Sunday morning.
"We thank passengers for their understanding," she said.
"The safety of easyJet's passengers and crew is our highest priority."