A United Airlines pilot was spotted taking a nap out of uniform in first class on a flight from the US to Scotland.

Passengers witnessed the unnamed pilot sleeping during the seven-hour flight from Newark, New Jersey, to Glasgow on 22 August, and one even took a picture of the incident.

The passenger responsible for the snap, a retired police officer, told the Daily Record: “Surely if pilots are in need of a rest mid-flight, they should do it away from the passengers.

“I’ve travelled to the US many times and have never witnessed this.”

He said the pilot had changed out of uniform in the toilet, slept for an hour and a half, and then changed back before radioing for access to the cockpit.

The first officer reportedly had a nap afterwards.

“Police officers get a hard time when they are photographed sleeping in a patrol car,” said the passenger.

“I don’t think the captain of a flight packed with hundreds of people should be in such a vulnerable position.”

The flight was under the control of a three-man cockpit crew, so passengers’ safety was never in question.

United Airlines said in a statement: “On transatlantic flights, pilots are required to take a rest break.

“This aircraft is operated by a cockpit crew of three and this pilot was on his rest period.”

Aviation deals website The Points Guy wrote an article backing this up, saying that on longer legs, such as those across the Atlantic, it’s actually required by law that pilots take rest breaks.

It says: “According to the Code of Federal Regulations, or CFR, when there are three or more pilots operating a flight, each may not exceed more than eight hours of flight deck duty in any 24-hour period.

“The flight in question, United 161, from Newark (EWR) to Glasgow, Scotland (GLA), typically has a flight time of less than seven hours, so two pilots could operate that eastbound leg. The return can exceed eight hours of cockpit time, however, so an additional pilot is required - and they can’t spend rest time on the flight deck.”

On larger planes, pilots can take their rest breaks far from passengers’ view, but on the smaller 757-200, which United flies between Newark and Glasgow, “one of the 16 lie-flat business-class seats is reserved specifically as a crew rest, with pilots completing mandatory rest requirements during the over-water portion of the flight.”

It’s not the first time a pilot has come under fire for their behaviour on board a flight.

In January, two Jet Airways pilots left the cockpit while “having a fight”. A male pilot reportedly slapped his female colleague before the two left the controls unattended with 323 passengers and 14 crew members on board.

After the captain left the cockpit, she was followed by the co-pilot as he asked her to return, in direct contravention of aviation rules, which state that one pilot must be in the cockpit at all times during flight. He then used the intercom to ask cabin crew to persuade the captain to return, alerting passengers to the situation.