Boeing has failed to win the backing of US regulators in a debate over whether or not to move wiring bundles on the grounded 737 Max.
Last month, there were concerns that a disagreement between US and European regulators on whether to relocate electrical wiring could frustrate the Max’s return to service.
But the Federal Aviation Administration (FAA) is believed to have adopted the same position as its European counterpart on the wiring issue.
Boeing does not believe it is necessary to move wiring bundles on its 737 Max but regulators think they need to be moved for safety reasons, warning that they could otherwise short circuit.
It is now up to Boeing whether to move the wiring bundles or try to convince the FAA to reconsider its position, although the latter is considered unlikely.
Boeing’s Max is expected to make its return in the summer but a key certification flight is not expected until next month. It was grounded a year ago after two fatal crashes within five months.
The planemaker has previously said in talks with the FAA that the same wiring bundles in the Max are present in the 737 NG, which has been in service since 1997 without reporting any wiring issues.