A pilot continued flying as he thought his co-pilot who died in the cockpit was joking.

The pilot thought his colleague, a flying instructor, was pretending to be asleep when shortly after takeoff in Blackpool the instructor’s head rolled back.

The pilot knew the 57-year-old instructor well and thought he was just pretending to take a nap while the pilot flew the circuit, and so did not think anything was wrong at this stage.

However, when he landed the plane and his co-pilot was still resting on his shoulder and not responding, the pilot realised something was amiss.

He signalled to the airport fire crew, who happened to be working on the apron and came to assist.

A post-mortem concluded that the instructor died from acute cardiac failure.

The Air Accidents Investigation Branch (AAIB) investigated the incident so that “lessons could be learned”.

The report found the pilot who died had passed a medical four months earlier and was able to land the aircraft safely, adding that "the outcome could have been different" on a different flight.

The instructor had agreed to join the short journey aboard a G-BORL light aircraft around Blackpool Airport in June last year because two pilots were needed for the flight due to the weather conditions.

The report found there was no indication that the instructor was unwell.

“People who had spoken to him on the morning of the incident said he was his normal cheerful self and there were no indications that he was feeling unwell,” the report said.

“The three people who had flown with him for the trial lesson just prior to the incident flight said he seemed well and nothing abnormal had occurred.”

The AAIB report concluded that current medical assessments were acceptable but risks "can never be reduced to zero".

It added that cardiac events are a “significant cause of sudden incapacitation, including death” in the general population as well as among aviation personnel.

“In multi-pilot commercial air transport the safety risk is mitigated by the second pilot. However, the risk remains for single-pilot operations,” the report said.