Flights were temporarily grounded at Stansted Airport after RAF jets were scrambled to escort a Ryanair flight.
A spokesman for the airport, in Essex, said police were on the scene after the passenger plane was diverted from its route between Kaunas, Lithuania, and Luton Airport, in Bedfordshire.
He added all flights had now resumed after being held for about 10 minutes from 8.55am on Wednesday.
He said: "Flights were briefly held while RAF Typhoons escorted the plane in. All flights are now operating as normal. It was literally a momentary pause."
A Ryanair spokesman said: "This flight from Kaunas to London Luton diverted to London Stansted in line with procedures after Lithuanian authorities received a suspected hoax security alert.
"The aircraft landed normally at Stansted and customers will be transferred to Luton by coach when cleared to do so."
The jets were sent from RAF Coningsby, Lincolnshire to intercept the flight, the Ministry of Defence said.
A sonic boom echoed across the Suffolk skyline when the jets were scrambled, Suffolk Police confirmed.
An RAF spokesman said: "The RAF can confirm Quick Reaction Alert Typhoon aircraft were launched this morning from RAF Coningsby to intercept a civilian aircraft.
"The aircraft was safely escorted to Stansted Airport. The Typhoon aircraft were authorised to transit at supersonic speed for operational reasons; any inconvenience caused to local residents is regretted."
The so-called Quick Reaction Alert is said to be a routine part of the RAF's role in defending UK airspace. Aircraft responding to QRAs are kept on high alert and can take off "within minutes", the air force said, and are often used to intercept unidentified planes.
Typhoon pilots at RAF Coningsby and RAF Lossiemouth are on standby 24 hours a day to defend UK airspace.
Stansted is a designated airport for dealing with hijacks and major security alerts. Such incidents are normally dealt with in a remote part of the airfield to the north-west of the terminal building.
An RAF Typhoon jet escorted a Pakistan International Airlines plane to Stansted in February.
An airline spokesman at the time said UK authorities had "received some vague security threat through an anonymous phone call".
Essex Police said that the incident was "not believed to be a hijack situation or terror matter".