US aviation safety officials ordered unusual inspections of a sample of four Boeing 787s amid questions about quality issues on the company’s carbon-fiber widebody jetliner. The Federal Aviation Administration wrote to Boeing on January 11, telling the company it was going to conduct Certificates of Airworthiness inspections on four 787s, according to a letter reviewed by Bloomberg News. The final review before an aircraft is handed over to buyers, known as an AC, has traditionally been delegated to Boeing’s own employees. “The FAA is taking a number of corrective actions to address 787 production issues,” the agency said in an emailed statement. “One of the actions is retaining the authority to issue ACs for four specific aircraft. We can extend the AC retention to other aircraft if we see the need.” The agency didn’t say in its statement whether the inspections had begun or what, if anything, had been found. FAA also didn’t specify what “production issues” it had discovered. Boeing rose 3.28 per cent to close at $263.59 Wednesday in New York. The stock dropped 3.9 per cent on Tuesday, the sharpest decline on the Dow Jones Industrial Average, after Bloomberg News reported that the company was testing cockpit windows on some 787s. “We are encouraged by the progress our team is making on returning to delivery activities for the 787 programme,” Boeing said on Wednesday in an emailed statement. “We have engaged the FAA throughout this effort and will implement their direction for airworthiness certification approval of the initial airplanes as they have done in the past.” The Chicago-based manufacturer hasn’t delivered any 787 models since October as it searches for tiny defects near where the fuselage sections were joined. Boeing mechanics and engineers are working to restart 787 Dreamliner deliveries by the end of this month, in line with what executives promised during a January earnings call. Boeing and FAA have had tense relations in the past two years in the wake of the twin fatal crashes of the 737 Max that led to its 20-month grounding. Several additional flaws were discovered on the 737 Max during the grounding, and the agency has brought multiple civil enforcement actions against the company recently. Boeing agreed to pay $6.6 million on February 25 because it failed to adhere to a 2015 agreement to improve its safety practices, including on its production lines. Under longstanding practice, the FAA typically deputises Boeing employees to inspect planes as they come off the assembly line to ensure they are properly made and can be legally sold. FAA inspectors occasionally conduct a handful of the reviews to ensure they remain properly trained. The FAA has issued a small number of airworthiness certificates for 787 Dreamliners every year since 2017, according to a person briefed on the matter. The annual checks have varied between two and four aircraft annually, the person said. The AC approvals were being retained by FAA in this case as a result of the unspecified issues discovered on the 787 production lines, FAA said. The FAA also retained the sign-offs for all 737 Max jets coming of Boeing’s assembly line starting in November 2019 after debris such as rags and tools were discovered in the planes during inspections. Boeing has been forced to store more than 80 Dreamliners as they work with suppliers to identify the source of manufacturing flaws in the plane.