Boeing faces new hurdle in 737 MAX electrical grounding issue: Sources

 The extra analysis injects new uncertainty over the timing of when Boeing's best-selling jetliner would be cleared to fly by the U.S. Federal Aviation Administration (FAA)

By Eric M. Johnson, David Shepardson, and Tracy Rucinski

SEATTLE/WASHINGTON/CHICAGO (Reuters) - U.S. air safety officials have asked Boeing Co to supply fresh analysis and documentation showing numerous 737 MAX subsystems would not be affected by electrical grounding issues first flagged in three areas of the jet in April, two people familiar with the matter told Reuters.

The extra analysis injects new uncertainty over the timing of when Boeing's best-selling jetliner would be cleared to fly by the U.S. Federal Aviation Administration (FAA).

The electrical problems have suspended nearly a quarter of its 737 MAX fleet.

U.S. airlines have said they expected Boeing to release the service bulletins as soon as this week that would allow them to make fixes and soon return the planes to service, but this latest issue will likely push that timeline back.

"We continue to work closely with the FAA and our customers to address the ground path issue in affected 737s," a Boeing spokeswoman said.

Asked about the status of the planes, an FAA spokesman said "we are continuing to work with Boeing."

Airlines pulled dozens of 737 MAX jets from service early last month after Boeing warned of a production-related electrical grounding problem in a backup power control unit situated in the cockpit on some recently built airplanes.