Royal Air Force jets were scrambled to intercept a passenger plane after reports of a "security threat".
The Ryanair flight from Vienna, Austria, was intercepted by RAF Typhoons on its way to London Stansted Airport.
Two men were detained by police after the flight was intercepted, but they have now been released.
In a statement, the Eastern Region Special Operations Unit said: "Officers investigating reports of a suspicious device on a flight landing at London Stansted Airport on Sunday have concluded their inquiries.
"Following reports of a suspicious device in the bathroom of a plane arriving from Vienna, Austria, shortly after 7pm, Counter Terrorism Policing officers from the Eastern Region Special Operations Unit detained two men under Schedule 7 of the Terrorism Act (2000).
"After examination by specialist investigators, the object was found not to be of concern. Officers spoke with the two men and neither were considered to have committed any offences."
The RAF confirmed that Typhoon fighters from RAF Coningsby in Lincolnshire were launched "to intercept a civilian aircraft" and that the aircraft "was escorted safely to Stansted".
A Ryanair spokesman said the crew of the flight from Vienna to the Essex airport had been alerted to a "potential security threat on board".
He added: "In line with procedures, the captain informed UK authorities and continued to London Stansted, where the aircraft landed normally and taxied to a remote stand where passengers disembarked safely.
"Passengers in London Stansted waiting to depart to Vienna were transferred to a spare aircraft to minimise the delay to their flight."
Detective Superintendent Andy Waldie said: "We understandably take any reports of suspicious objects or behaviour on flights very seriously and thankfully on this occasion there was no cause for concern."
Cover image: A library picture of an RAF Typhoon jet (Picture: MOD).