Two RAF Typhoon jets were scrambled to a "security alert" involving a Ryanair passenger plane this evening.
The Boeing 737-800 from Krakow to Dublin was diverted to land at London Stansted under military escort at around 6.40pm.
The RAF ordered its Quick Reaction Alert crews to intercept the aircraft after a reported "bomb scare".
A Ryanair spokesperson told the Standard: "A Ryanair flight from Krakow to Dublin this evening (13 JUL) discovered a note in one of the toilets claiming that there were explosives on board.
"The captain followed procedure by alerting the UK authorities and diverted to the nearest airport (Stansted) where the plane landed normally, but was taxied to a remote stand where passengers disembarked safely."
The Ministry of Defence (MoD) said the Typhoon fighter jets have since returned to RAF Coningsby in Lincolnshire but police are still dealing with the flight on the ground.
Essex Police said in a statement: "A flight from #Krakow to #Dublin was diverted to #Stansted Airport at around 6.40pm on Monday 13 July due to reports of a security alert.
#FR1902, Krakow-Dublin, squawking 7700 and descending over the UK. No reason known at this time. https://t.co/xPhhd2MDvU
For more information on ‘Squawking 7700’ please see https://t.co/nW7vZ4JgMF pic.twitter.com/37qkzYbtLO— Flightradar24 (@flightradar24)July 13, 2020
"The plane is currently at the airport and officers are making enquiries. We’ll bring you more information when we can."
The force later said: "We have now safely brought off all the passengers from the plane. The plane remains in an isolated area at Stansted and our enquiries are ongoing."
An MoD spokesman told the Standard: "Two Typhoons were dispatched from RAF Coningsby to inspect a Ryanair passenger flight that has now been grounded at Stansted and Essex Police are on hand at the moment.
"It was all escorted escorted safely and there were no issues after that point."
Stansted Airport confirmed police were still dealing with the incident but could not give any further information.
— Andy Kirby (@AndrewJohnKirby)July 13, 2020
Ryanair added in a statement: "The aircraft and passengers are being checked by the UK police who will decide when they may travel onwards to Dublin on a spare aircraft.
"Passengers in Dublin waiting to depart to Krakow are being transferred to a spare aircraft to minimise any delay to their flight.
"Ryanair apologises sincerely for the delay and inconvenience caused to those affected by this diversion".
Earlier unconfirmed reports had suggested that communications had been lost with the pilot.