After a string of delays in delivering aircrafts to Europe’s biggest low-cost airline, O’Leary hit out at Boeing leaders in an expletive-laced conference call with analysts on Monday, saying the company executives need either a “reboot or a boot up the a**.”

Ryanair is one of Boeing’s largest customers, using only the plane manufacturer’s 737-800 aircraft for its 300 plus plane fleet, and O’Leary has been relying on an order of 737 MAX planes to propel the airline’s growth out of pandemic, where the company had to write off €815 million in losses in 2020 alone.

But as COVID-19 recedes into the distance and summer tourism returns in full swing, O’Leary claims the company’s expansion plans have been hurt by Boeing’s failure to deliver, adding some aircraft that were due in April are now set to arrive in June.

“We’re a willing customer, but we’re struggling with slow deliveries and an inability to do a deal on new aircraft,” he said.

“At the moment, the Boeing management is running around like headless chickens, not able to sell aircraft.

“I can understand why there may be various challenges manufacturing new aircraft, but aircraft that you built and made two years ago that all you had … to do was put petrol in them and f***ing fly them to Dublin, really I don’t understand why you’re taking two to three-month delays on that.”

The Irish CEO said they were now looking to source secondhand Airbus and 737 aircrafts, saying the used market was making the option more attractive.

“They are losing market share hand over fist to Airbus and don’t seem to be responding appropriately,” O’Leary said in the conference call, citing other long-term Boeing customers who have switched to Airbus including U.K.’s Jet2 and Australia’s Qantas Airways.

“Either the existing management needs to up its game, or they need to change the existing management, would be our view of life.”

“We’re very happy to work with existing management but they need to bloody well improve on what they’ve been doing delivering to us over the last 12 months.”

Ryanair was in talks with Boeing to purchase around 250 MAX 10 planes—in a deal worth around $33 billion—but talks collapsed last September after pricing negotiations fell through.

O’Leary said that he was willing to restart discussions with Boeing for a new MAX 10 order, but he had not heard anything back from the company.

“You wonder what the hell their sales team has done in the last two years,” O’Leary said.

“Frankly most of them seem to sitting at home in their f***ing jimjams working from home instead of being out there selling planes to customers.”