Boeing (BOE, Chicago O'Hare) has won approval from US regulators for a fix of an electrical grounding issue that affected about 100 B737-8s, clearing the way for their quick return to service after flights were halted in early April, Reuters reports.

An FAA official confirmed the agency had approved the service bulletins and associated instructions, after Boeing had sent two bulletins to affected airlines on May 12, advising them on the fixes.

"After gaining final approvals from the FAA, we have issued service bulletins for the affected fleet," Boeing told Reuters. "We are also completing the work as we prepare to resume deliveries."

Boeing on April 8 had notified the FAA that it had recommended to 16 operators of a specific group of recently-built B737 MAX aircraft to temporarily remove them from service to address a manufacturing issue that could affect the operation of a backup power control unit in the cockpit. The recommendation was made to allow for verification that a sufficient ground path existed for a component of the electrical power system.

The problem, which halted delivery of new aircraft, was then found in two other places on the flight deck, including the storage rack where the control unit is kept and the instrument panel facing the pilots. Reuters reported on May 4 that the FAA had asked Boeing to supply fresh analysis showing numerous B737 MAX sub-systems would not be affected by electrical grounding.

The electrical issue reportedly emerged after Boeing had changed a manufacturing method to speed up the production of the jetliner, which was approved to return to service in November 2020 after being grounded for 20 months following two fatal crashes in five months that killed 346 people.

The top three US B737 MAX operators - Southwest Airlines, American Airlines, and United Airlines - removed more than 60 of the type from service after the notice from Boeing.

The FAA said other carriers affected included Cayman Airways, Copa Airlines, GOL Linhas Aéreas Inteligentes, Icelandair, Minsheng Financial Leasing, Neos, Shandong Airlines, SilkAir, SpiceJet, Sunwing Airlines, TUI fly (Germany), Turkish Airlines, Valla Jets Limited, WestJet, and Xiamen Airlines.

FAA Administrator Steve Dickson had told US lawmakers that the electrical issue, which had grounded about a quarter of the MAX fleet, would need a "pretty straightforward fix." Dickson also said he was fully confident in the safety of the MAX.

The regulator had daily meetings with Boeing to discuss the MAX’s performance, Dickson said. In February, the FAA said it was tracking all B737 MAX aircraft using satellite data under an agreement with air traffic surveillance firm Aireon LLC.