A budget airline is to be prosecuted after allowing a 757 jet to fly “illegally” to America with faulty instruments.

The case against Flyglobespan, which flies more than 2.2m passengers a year to 30 destinations, will be the first criminal prosecution against a British airline for more than a decade.

The Sunday Times has established that the transatlantic flight is one of a number of alleged safety breaches being investigated by the Civil Aviation Authority (CAA).

The regulator is also looking into cases where two aircraft were flown without official clearance after one was damaged by lightning and another was hit by an airport vehicle.

The disclosures come amid increased concern that low-cost carriers, which already operate on tight margins, may cut corners on maintenance as profits are hit by rising oil prices.

Flyglobespan, which flies from airports such as Gatwick, Manchester and Glasgow, is run by Tom Dalrymple, a 63-year-old Scottish multi-millionaire. It is understood that Dalrymple, who is worth £75m according to The Sunday Times Rich List, was interviewed under caution by the CAA in March.

The inquiry centred on a 12-year-old Boeing 757 which flew between Liverpool, Knock, in the west of Ireland, and New York. As the jet was taking off from JFK airport on June 28 last year both its engine pressure ratio gauges failed. The pilot reported the faults when he reached Liverpool.

The plane, which carries more than 200 people, should have been grounded until at least one of the gauges had been fixed. But the airline authorised it to fly back across the Atlantic with neither gauge functioning.

The gauges measure engine thrust, which is critical during take-off. They are on a mandatory list of equipment which has to be operational if the 757 is to be certified as airworthy.

Graham Sturrock, a former pilot who advises airlines, said that flying without the gauges reduces the safety net if other equipment fails. “It also increases the pilot’s workload and the chance of pilot error,” he said.

When the plane reached New York it was grounded until it was repaired. The problem should have been reported to the CAA within four days but it was left to the American regulator to report it three months later.

It is understood the airline has admitted sanctioning the flights and has replaced two managers.

The airline was served three summons to appear before City of Westminster magistrates in July to answer criminal charges that included, with regard to the gauges, a failure to notify the CAA of a matter which could endanger an aircraft, its occupants or any other person. The offence carries an unlimited fine.

The prosecution comes after a difficult period for Flyglobespan, which had been a rising star of the airline industry. Dalrymple’s business was originally a travel agency but he diversified into airlines in 2002, picking up airport spaces vacated after the 9/11 terrorist attacks. His group’s turnover is £280m and it employs 1,500 people.

Last October the CAA suspended its Etops licence for two weeks after identifying undisclosed problems. Etops permits an airline to fly over large expanses of water; without it, Flyglobespan could not travel over the Atlantic. Instead, it had to take a route via Iceland and Greenland to be within an hour of land in case of emergency.

There was further bad publicity in January when an engine burst into fire on a flight from Orlando, Florida. Passengers reported hearing loud bangs and seeing flames. “I thought we were going to die,” said one.

The wider CAA investigation has looked at allegations that two damaged aircraft were flown for repair late last year without first seeking the necessary permit from the regulator.

One had been hit by a baggage vehicle. The other, which suffered a suspected lightning strike, is thought to have made six flights before being repaired.

Experts say great care should be taken after a plane has been involved in an incident where the extent of the damage is not fully known. “The point is that you are potentially flying a bomb,” said one industry official.

Last week Norman Baker, the Liberal Democrat spokesman for transport, voiced his concerns about low-cost airlines hit by the soaring price of oil: “The consequence of that is we all have to be very vigilant that safety cuts are not made in order to keep accounts in the black.”

This weekend the CAA confirmed that it had issued the summonses against Flyglobespan over the flight to New York.

Flyglobespan confirmed that it had been in discussion with the CAA regarding “some alleged issues from last year’s programme”. It said that it has since made changes to its fleet, senior management, engineering and reporting procedures and is operating with full CAA approval.

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