DUBLIN (Reuters) - Ryanair Group CEO Michael O'Leary said on Saturday a prolonged Boeing 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 largest customers, was supposed to receive 30 737 MAX aircraft before summer 2025 but Boeing's operational issues had already brought that number down to 25.

But now, with this week's Boeing's 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 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 factories in the Seattle area that assemble Boeing's MAX, 777 and 767 jets.

Boeing 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 two to three years to get back on track.

Boeing 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)