Boeing was plunged into crisis after a panel blowout on an airborne Max 9 plane above Portland in Oregon in January. 

Unlike other disasters for Boeing in recent years, no one was killed in the incident, but huge safety concerns about the safety of its manufacturing processes pushed regulators to swoop on the Seattle-based manufacturer and on its US suppliers. 

Production limits were subsequently imposed on the family of its Max planes.

The crisis could deepen further and for Boeing airline customers for existing orders and for other planes in the Max family that have yet to be certified, in particular the Max 10 jet.

“Certification of remaining Boeing 737 Max aircraft models could also become challenging,” Morningstar said, without specifically referring to Ryanair which last year placed a $40bn (€36.5bn) order for the yet-to-be-certified Max 10s.

The deal includes a firm commitment for 150 of the planes and an option for 150 more, with the first planes due for delivery from 2027.

“Both airline and lessor customers have expressed concern and frustration with Boeing’s ongoing issues, which could affect business relationships and future product orders,” the ratings firm said.

Morningstar said that Delta Air Lines in the US has extended its expected Boeing 737 Max 10 deliveries to 2027 because of certification issues.

It also referred to Ryanair having cut its summer 2024 schedule as it now expects fewer deliveries from Boeing of different type of Max planes.

“Combining Boeing’s recent issues with existing post-coronavirus supply chain issues at aircraft manufacturers, aircraft delivery delays are further worsening and may persist for a few years,” according to the Morningstar analysts.

“This could affect the airline sector in several ways, including the sector’s growth being affected because of lower capacity; operational disruptions as airlines may need to revisit flight schedules, particularly for the upcoming summer season; airfares may rise further because of demand-supply imbalance; and decarbonisation targets could be missed because of delays in fleet modernisation,” the analysts said in the commentary.

The commentary cites the move by United Airlines to offer pilots a voluntary unpaid leave, while Southwest Airlines has halted recruitment.

Morningstar also estimates that Air India, Alaska Air — which operated the flight involved in the January Max 9 incident, and VietJet Air have large numbers of unfilled passenger jet orders with Boeing.

However, the analysts said that the Boeing supply woes “could be slightly positive for the struggling cargo sector”.