Boeing must hold out against a strike by 33,000 workers even if it means aircraft deliveries are held up by several months, Ryanair boss Michael O’leary said.

Mr O’Leary said he backed Boeing chief Kelly Ortberg’s decision to abandon talks after the machinists union rejected a sweetened 30pc pay offer.

The Ryanair boss said: “They have to see out this strike and if that means all of our deliveries get delayed by a couple of months, frankly we would support that.

“They’ve said fine, we’ll walk away from the negotiations because the negotiations are going nowhere. There’s nothing else they can do at the moment other than play the longer game.”

He said the International Association of Machinists and Aerospace Workers (IAM) had been “mad” to reject the improved deal and that both Mr Ortberg and commercial jets chief Stephanie Pope were “doing a really good job in difficult circumstances on the ground”.

He also praised the decision of both executives to base themselves in Seattle “so you now have people living on top of the shopfloor.” A refusal to relocate from Boeing’s offices near Washington DC had been a “great weakness of previous management,” he said.

Ryanair is Boeing’s biggest European customer with 500 of the US manufacturing giant’s aircraft in its fleet and hundreds more on order. Mr O’Leary’s support may encourage Mr Ortberg, who took over in August, to dig in as the union presses for a 40pc raise.

Boeing last month made what it called its “best and final” offer to workers, proposing the 30pc pay increase over four years. After talks reached a stalemate, it withdrew the plan before announcing that it would cut 17,000 jobs or 10pc of the global workforce.

Mr O’Leary said Boeing had been unfortunate in having to negotiate its first pay settlement in years while in the grip of a production crisis that took hold after a panel blew out of an Alaska Airlines 737 Max plane in January.

The incident revealed endemic quality control issues at the company and led regulators to cap build rates for the suspect jet.

The Ryanair chief said: “The timing of the existing contract running out was unfortunate given the state that Boeing is in, and that’s being exploited by the unions. Even if they do offer more, the unions won’t agree to a deal at the moment.”

He also claimed that the IAM had also been “incompetent” in negotiating a 25pc settlement that it agreed to put to workers, only for it to be rejected in a formal vote.

Almost 95pc of the union members voted to reject Boeing’s initial offer, with 96pc of those who voted backing strike action.