F15s are often heavily armed

Passengers on board the Britannia Airways passenger jet, which was heading to Cyprus from Birmingham airport, were unaware of the incident.

The F15 was flying from RAF Lakenheath in Suffolk, the newspaper said.

The Civil Aviation Authority has said the incident was so serious it was referred directly to the Air Accidents Investigation Branch.

"The report from the pilot or the controller must have suggested it was a particularly serious incident for this to happen," said a CAA spokeswoman.

She added: "The incident took place about eight miles west of Daventry in Northamptonshire at 10.17am.

"The Boeing 757 was en route for Paphos, Cyprus and was receiving an air traffic control from London area control at West Drayton."

A spokeswoman for Britannia Airways said none of the passengers were aware of the incident because the plane was passing through a cloud at the time.

"We cannot comment on the details of the incident while an investigation is under way, but we can confirm that a Britannia Airways plane was involved and that it had 234 passengers on board," she said.

The revelation comes in the week that the government succeeded in passing controversial plans to part-privatise the air traffic control system.