Michael O’Leary, chief executive of Ryanair Holdings Inc., tore into Boeing Co. during an earnings call Monday, blasting the plane-maker’s “very poor management” and calling for a shakeup at the top.

“At the moment, we think Boeing management is running around like headless chickens, not able to sell aircraft, and then even the aircraft they deliver, they’re not able to deliver them on time,” O’Leary said on a post-earnings conference call with analysts, according to a FactSet transcript.

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Dublin-based Ryanair, Europe’s largest budget airline, has ordered hundreds of planes from Boeing, but deliveries have been delayed, forcing the airline to scale back its schedule. Last fall, Ryanair ended negotiations with Boeing over an order for Max 10 aircraft over a price dispute.

O’Leary made it clear Monday that he blames Boeing.

“The management of Boeing in Seattle is very poor,” O’Leary said Monday’s call. “We’re their largest customer but they need a reboot or a boot up the ass somewhere in Seattle and hopefully, [CEO Dave] Calhoun will deliver it.”

O’Leary said Boeing had agreed to deliver a number of 737 Max airliners by this spring, but failed to come through.

“It’s probably cost us about 600,000, 800,000 seats in May and June, which is disappointing and still unexplained by Boeing,” he said.

O’Leary was particularly frustrated by the delay because he said the planes were already manufactured years ago.

“All you had to kind of do is put petrol in them and fly them to Dublin. Really, I don’t understand why it’s taking you – you are taking two or three month delays on that,” he said. “But it is redolent of, I think, a very poor management performance in Seattle both in competing for market share against Airbus and in just honoring your commitments in delivering the planes you promised to deliver.”

“So, Boeing need a management reboot in Seattle and either the existing manager needs to up its game or they need to change the existing management,” O’Leary said.

Still, he said Ryanair would be happy to work with Boeing’s existing management, “If they get their s*** together. … but they need to bloody well improve on what they’ve been delivering to us over the last 12 months.”

“We’re a willing customer, but we’re struggling with slow deliveries and an inability to do a deal on new aircraft despite the number of white tails that are sitting on the ground in Seattle,” O’Leary said. “You wonder what the hell their sales team have done for the last two years. And frankly, most of them seem to be sitting at home in their jim-jams working from home instead of out there selling planes to customers.”

Last week, Boeing reported its deliveries slipped in April, and its shares have sunk since posting a big first-quarter earnings miss. Boeing shares BA, -2.48% are down 31% over the past month and off nearly 40% year to date.

Ryanair’s American depository receipts RYAAY, -2.39% are down about 21% year to date, while its Irish-listed shares RYA, -0.18% are off about 10% this year.