Boeing could have to delay deliveries of more of its bestselling 737 Max planes after a supplier found new production glitches, adding to pressure on the beleaguered US manufacturer. The aircraft maker will have to conduct work on about 50 undelivered planes after its supplier Spirit AeroSystems discovered two holes drilled incorrectly. Boeing’s share price fell by 2.2% in early trading on Monday, while Spirit’s fell by 3.9%. The latest mishap comes with Boeing under severe scrutiny over its manufacturing processes after part of the fuselage fell off a plane last month. A panel plugging an unused door hole fell from an Alaska Airlines flight shortly after takeoff, forcing the plane to turn back to Portland, Oregon, although there were no serious injuries. Until the latest incident, Boeing had been trying to increase production of its 737 Max after years in the doldrums when two planes crashed because of design flaws. The model was grounded for nearly two years after 346 people died onboard Lion Air flight 610 in October 2018 and Ethiopian Airlines flight 302 in March 2019. However, Boeing has come under pressure from its airline customers after the Alaska incident highlighted apparent continued failures in its safety processes. Tim Clark, the head of Emirates Airlines, has become the latest airline leader to call for significant change at Boeing. Speaking in an interview with the Financial Times, published on Sunday, he said Boeing was in the “last chance saloon” after a “progressive decline” in standards. Clark said Boeing had to “instil this safety culture which is second to none” and “get their manufacturing processes under review so there are no corners cut”. He mirrored a regular criticism of Boeing from some in the industry that it had focused too much on financial returns. Boeing’s board, he said, needed to prioritise production: “Not: ‘What is the return on investment? What is the bottom line? What is the free cashflow? What is the shareholder value? What is the share value? What is my bonus?’ No, that will come if you do it right in the first place.” As of Friday, the incorrectly drilled holes had been found in 22 fuselages out of 47 inspected up to that point, spread between Boeing and Spirit, and may exist in some 737s in service, according to sources cited by Reuters. An employee from Spirit AeroSystems, which is the sole supplier of the fuselage for the 737 Max, reportedly discovered that the holes were too close to the edge of the piece of metal in a window frame. A Boeing spokesperson pointed to a public letter to Boeing staff from the chief executive of the commercial planes arm, Stan Deal. He wrote: “This past Thursday, a supplier notified us of a non-conformance in some 737 fuselages. I want to thank an employee at the supplier who flagged to his manager that two holes may not have been drilled exactly to our requirements.” Deal wrote that the incorrect holes were “not an immediate flight safety issue and all 737s can continue operating safely”. In response to criticisms from airlines, Boeing referred to comments last month by the chief executive, Dave Calhoun, who said: “We understand why they are angry and we will work to earn their confidence.” He said the manufacturer had “taken close care not to push the system too fast”, but had “more work to do”. A Spirit spokesperson said: “A member of our team identified an issue that does not conform to engineering standards. Once notified, we began immediate actions to identify and implement appropriate repair solutions. We are in close communication with Boeing on this matter.” Deal wrote that the incorrect holes were “not an immediate flight safety issue and all 737s can continue operating safely”. In response to criticisms from airlines, Boeing referred to comments last month by the chief executive, Dave Calhoun, who said: “We understand why they are angry and we will work to earn their confidence.” He said the manufacturer had “taken close care not to push the system too fast”, but had “more work to do”.