Boeing Co sent all affected carriers service bulletins late on Wednesday on how to address the production issue, which had affected 109 planes worldwide. The Federal Aviation Administration had signed off on the service bulletins, Reuters first reported late on Wednesday.
The action was a relief for American carriers, which had anxiously awaited the green light to get the planes back into the air before the traditional late May start to the summer travel season. U.S. demand for air travel has risen as the COVID-19 pandemic has waned in the United States.
The halting of flights by about a fourth of the MAX fleet came after the plane was grounded for 20 months following two fatal crashes. The FAA lifted that grounding order in November after Boeing made a number of software and training upgrades.
The electrical problem being repaired did not cause any in-service failures, the FAA noted.
United spokeswoman Leslie Scott said on Thursday the airline expects its "Boeing 737 MAX aircraft to return to service in the coming days as we complete our inspection process and ensure those aircraft meet our rigorous safety standards."
American Airlines said it would begin making required changes and anticipates "all affected aircraft will begin safely returning to service in the upcoming days."
Southwest Airlines, which has 32 affected planes, said it estimates the work will take two to three days per aircraft. The airline said it hoped to begin work within the next several days, and estimates it will take about three weeks to complete the work.
Shares in the airlines and Boeing were up 1.8% to 2.9% in late morning trading.
FAA Administrator Steve Dickson told U.S. lawmakers on Wednesday the electrical issue, which had grounded about a quarter of the MAX fleet, would need a "pretty straightforward fix."
Airlines removed dozens of 737 MAX jets from service in early April after Boeing warned of the electrical problem, linked to a backup power control unit in the cockpit on planes built since early 2019.
The problem was then found in two other places on the flight deck: the storage rack where the control unit is kept and the instrument panel facing the pilots.
The FAA said in statement last month that other carriers affected by the electrical issue were Cayman Airways, Copa Airlines, GOL Linhas Aereas, Iceland Air, Minsheng Leasing, Neos Air, Shanding Airlines, SilkAir, Spice Jet, Sunwing Airlines, TUI, Turkish Airlines, Valla Jets Limited, WestJet Airlines and Xiamen Airlines.
(Reporting by David Shepardson; Editing by Chizu Nomiyama and Jonathan Oatis)
By David Shepardson