Boeing's grounded 737 Max plane may have flaws in its construction, US regulators said this evening.
The Federal Aviation Administration said that the plane maker had discovered potential problems with the leading edge slat tracks on the plane and the 737 Next Generation.
The leading edge slats are flaps on the front of a wing which allow the plane to lift or dive.
The faults affect 148 parts which are manufactured by a Boeing supplier, the FAA said. They are thought to be installed on 133 NG and 179 Max planes worldwide.
"The affected parts may be susceptible to premature failure or cracks resulting from the improper manufacturing process. Although a complete failure of a leading edge slat track would not result in the loss of the aircraft, a risk remains that a failed part could lead to aircraft damage in fight," the FAA said in a statement.
This is the first sign of any mechanical fault in the Boeing 737 Max, which was grounded in March after two accidents in less than six months killed almost 350 people.
Until now the manufacturer has pinned its hopes on a software update and pilot training.
It is unclear whether the new discovery will set back its plans to get the aircraft back in the air, however the FAA said it will issue a directive which would mandate Boeing to find a remove the faulty parts. Airlines running the planes will be forced to do this within 10 days.
It comes as carriers today called on regulators across the world to coordinate over the future of the plane.
“Any rift between regulators is not in anyone’s interest,” said Alexandre de Juniac, head of the International Air Transport Association which represents 290 carriers around the world, and 80 per cent of all air traffic.
Airlines are worried that the industry could see a repeat of March’s bans, which rolled in at different times in different jurisdictions.
This could cause disruption to schedules and confusion among passengers.
Separately, Airbus today urged the leaders of airlines to back its calls for talks in a 15-year trade spat with US rival Boeing which has made the companies pawns in US and European trade relations.
The letter, seen by Reuters, was sent to a number of airline chief executives asking them to act now to avoid tariffs.
The US has threatened to impose the charges on $11bn (£9bn) of EU goods, while the bloc said it could retaliate with a $20bn list of products.
“If the tariffs are applied, the effects would include greatly increased costs to U.S. and European airlines, aerospace suppliers and manufacturers,” Airbus sales chief Christian Scherer wrote in the letter.
It said airline chiefs should “urge Boeing to enter into the negotiations proposed by the EU and Airbus”.