In a statement, Boeing said it had been informed by a supplier the issue related to two fuselage fittings, adding it was not an immediate flight safety issue. "The in-service fleet can continue operating safely," said Boeing. However, it confirmed customers should expert "lower near-term" deliveries of new Max aircraft.

Boeing added it had notified the US Federal Aviation Administration, with the FAA confirming it had "validated" Boeing’s assessment of the issue – including there being no immediate safety concerns based on the facts and data provided by the manufacturer.

The issue affects Max 7, Max 8 and Max 8200 models, not the whole range of Max aircraft. According to Reuters, Boeing delivered 111 Maxs in the first quarter and had been hoping to ramp up monthly deliveries to deliver at least 400 this year.

Production has struggled to keep up with demand for new aircraft post-Covid; Boeing hasn’t confirmed whether it will have to scale back its ambitions.

It is the latest in a series of setbacks for Boeing and the Max aircraft in recent years following two fatal crashes in October 2018 and March 2019, which claimed 346 lives. On both occasions, the same flight control system was found to be at fault. The issue has since been remedied.

Ryanair has 210 Maxs on order, one of the largest orders on Boeing’s books. It took delivery of its first Max in June 2021.