But the three men -- all British citizens -- were released after witness testimony about the conversation could not be verified, said police in Cologne, Germany.
The plane traveling from Ljubljana, Slovenia, to London was diverted to the western Germany city of Cologne on Saturday.
The men, ages 31, 38 and 48, were initially arrested for a possible "crime against the state," police and prosecutors said in a joint statement Sunday.
Passengers alerted the flight crew because the men were "talking about terrorism-related content," Cologne police said.
When the aircraft landed in Cologne, all 151 passengers exited the plane through emergency slides. Some people suffered minor injuries, police and prosecutors said.
The men were taken to a police station, and the cabin crew and 17 passengers were brought in for questioning as witnesses.
A backpack belonging one of the men was examined by a bomb squad and destroyed in a controlled explosion, police said. It's unclear why the backpack was singled out.
Dogs were also called to search the plane for suspicious items, but no explosives were found. The aircraft was later cleared for use.
A few hours later authorities said the suspects, who were in Slovenia on a business trip for a British company, had been released.
Cologne police said their interrogation of the three men, plus an investigation of their belongings and the aircraft, did not reveal anything terrorism-related.
"There was no real situation of danger," Cologne police said in a statement.
Because the flight was rescheduled to continue Sunday, all passengers were given an overnight hotel stay and refreshments.
"We thank passengers for their understanding," the airline said. "The safety of easyJet's passengers and crew is our highest priority."