US giant Boeing has been labouring on a software fix and pilot training programme to in a bid to get its grounded Max 737 planes back in the skies, however, top US aviation safety officials cast doubt on the hopes of a smooth re-certification process for the company’s fastest-selling commercial jet ever.

A 787 jet that was commissioned by Air Canada and developed a fuel leak just ten months into service in 2015 had its records falsified by Boeing staff, reports CBC News.

Boeing Co self-disclosed the problem to the US Federal Aviation Administration (FAA) as soon as Air Canada notified the company of the malfunction.

According to the statement, the records had attested to the manufacturing work being completed in full, while this actually was not the case.

An audit, claims Boeing, concluded it was an isolated event and "immediate corrective action was initiated for both the Boeing mechanic and the Boeing inspector involved."

In response, Air Canada said it had inspected its fleet of 787 planes and failed to spot any other fuel leak issues.

When contacted for a comment, Air Canada spokesperson Peter Fitzpatrick said in an email to CBC News that all the aircraft are subject to regular and thorough inspections, adding:

“We maintain them in full accordance with all manufacturer and regulatory directives."

On the latest record-falsifying revelations, Mike Doiron of Moncton-based Doiron Aviation Consulting said: "Any falsification of those documents which could basically cover up a safety issue is a major problem."

Diron emphasised that in the aviation industry, these sorts of documents are crucial for ensuring the safety of aircraft and passengers, adding that even small fuel leaks are potentially dangerous.

The temperature on the internal parts of an aircraft's turbine engine can reach around 700 degrees, he said, and a flammable liquid like fuel ignites easily if there is a leak around the engine.

Air Canada introduced the 787 Dreamliner to its fleet five years ago, and it currently has 35 planes of this model.

Transport Canada said the incident involving falsified documents fell under the jurisdiction of the FAA and it is currently evaluating how ongoing aircraft safety validation efforts might be impacted by the new information.

The news comes as the US Department of Justice has asked Boeing to provide records of the assembling process of the 787 Dreamliner in South Carolina over "shoddy work", the Seattle Times reported Friday, citing sources close to the investigation.

The move comes as the authority is investigating the certification and design of another Boeing model - the 737 MAX.

The embattled American firm has been continuing its work with the US Federal Aviation Administration and other regulators in a bid to re-certify its 737 Max model and get it back in the skies.

Aviation regulators meeting in May were unable to estimate when the popular jet might again be allowed to fly, as Boeing now has 140 737 MAXs parked on its tarmac waiting for delivery, and has slashed monthly production to 42 planes from 52 previously.

The global 737 Max fleet was grounded in March following two fatal crashes. An Ethiopian Airlines 737 Max 8 plane crashed after takeoff in March, killing all 157 passengers and crew on board. That crash came just five months after the October 2018 crash of a Lion Air 737 Max 8, which killed all 189 people on board.

A malfunction of the plane’s automated flight-control system, called MCAS, has been suggested as a possible cause for the tragedies.