DUBLIN (Reuters) - Ryanair Group CEO Michael O'Leary said on Saturday a prolonged Boeing ( BA ) workers' strike may cut the number of aircraft it receives by next summer to 20 from an anticipated 25.

O'Leary said his low-cost Irish airline, one of Boeing's ( BA ) largest customers, was supposed to receive 30 737 MAX aircraft before summer 2025 but Boeing's ( BA ) operational issues had already brought that number down to 25.

But now, with this week's Boeing's ( BA ) workers' strike further threatening the airplane maker's turnaround, O'Leary said Ryanair might only receive 20 planes if the strike continues for three to four weeks.

"I have no doubt that Boeing ( BA ) will fix this strike," O'Leary told Ireland's Newstalk Radio. "It may take a number of weeks."

Workers have been protesting all week in Boeing ( BA ) factories in the Seattle area that assemble Boeing's ( BA ) MAX, 777 and 767 jets. 

Boeing ( BA ) has pledged to grow output by the end of the year, after wrestling with supply chain snags and operating a slower assembly line since a Jan. 5 in-flight blowout of a door plug on a 737 MAX 9 jet that heightened regulatory scrutiny.

O'Leary said it would likely take Boeing ( BA ) two to three years to get back on track.

Boeing ( BA ) and union negotiators will return to the bargaining table early next week as the two sides try to end a strike.

(Reporting by Conor Humphries; Writing by Catarina Demony; Editing by Ros Russell)