Jets were spotted roaring through the skies above Sheffield yesterday, with mystery surrounding their appearance.
Vincent Malone said he had seen around a dozen planes flying in close formation to the south of the city yesterday morning, at around 9am.
He shared this photo, showing some of the aircraft and their vapour trails standing out against the brilliant blue skies, which he took from Leighton Road in Gleadless Valley.
"We could see the vapour trails of around twelve jets flying very close together," he said.
"I've never seen it before and I think it's pretty obvious they were not passenger aircraft but military ones. Very strange!"
He shared his sighting on the Sheffield Forum community message board, where one person suggested the jets had been refuelling and others thought it may have been a trick of the eye, with the planes being trans-Atlantic flights that were actually many miles apart but appeared close together.
The most popular explanation was that they were part of a major military training event taking place at Leeds Bradford Airport from May 11 to this Friday, May 18, which the airport said would involve aircraft from the UK and overseas.
A spokesman for the airport said the planes seen over Sheffield yesterday morning could well be related to that operation, though he could not say for certain.
However, the Ministry of Defence has since referred the photos to an expert in the RAF, who suggested the planes were civilian aircraft rather than military ones.
A spokesman for the ministry said the expert confirmed the planes were not military ones, adding that although they appeared to be flying in formation they were actually at different altitudes.