The RAF has launched an investigation after a Tornado accidentally dropped a 14kg practice bomb during an exercise.
It was lost during a 90-minute training sortie from RAF Lossiemouth, which took the jet across north-east Scotland, Northumberland and out to sea.
The RAF said that even if the concrete device had survived the fall, it was "highly unlikely" to be dangerous - but people were warned not to touch it.
It has a fuse designed to emit smoke when it hits a target.
The dark blue bomb is 2.5ft long.
A spokesman for RAF Lossiemouth said anyone who found it should contact the police.
"Whilst incidents like this are extremely rare, we pride ourselves in being open and honest with the community and that is why we have issued this statement proactively," he said.
"Even if the practice bomb survived the fall, we would stress it is highly unlikely to represent a significant danger to the public."
He added that an investigation had been convened to determine the cause of the bomb's release.
Practice bombs are not live devices but are made to look and feel like real bombs.
The Ministry of Defence said they weighed the same as real ammunition and were carried on planes during training exercises to give pilots practice at flying with the necessary load.