Some Boeing 737 MAX Planes Temporarily Grounded After 'Potential' Issue

US aircraft manufacturer Boeing said on Friday it had recommended that 16 airlines flying its 737 MAX planes address a "potential electrical issue" in a new setback for the top-selling model.

Major carriers began temporarily removing some of their MAX planes from service after the aerospace giant flagged the electrical issue -- which is not a concern for all of the aircraft.

The potential problem requires "verification that a sufficient ground path exists for a component of the electrical power system," Boeing said.

Electrical systems must be grounded to avoid overloads that can cause serious failures.

Boeing shares fell Friday, although the likely impact of this latest issue appeared limited.

A note from the investment website Briefing.com said it was encouraging that a major Boeing customer, Southwest Airlines, expects only a minimal disruption.

"However, the news is another blow for customers' and investors confidence in the company," Briefing said.

Boeing managed to get the 737 MAX back in the skies late last year after it was grounded for 20 months following two fatal crashes, and recently announced an order for 100 of the aircraft as the airline sector begins to recover from the coronavirus pandemic.

The manufacturer discovered the latest issue on a plane in production "during normal build activity," a Boeing spokeswoman said.

It is "premature" to discuss the time needed to address the issue, and "could take a matter of hours or a few days" before planes are returned to service," she said.

Boeing did not say which airlines were concerned, nor did it specify the number of aircraft involved.

The company notified the US Federal Aviation Administration of the issue on Thursday night, an FAA spokesperson said.

"The FAA is in contact with the airlines and the manufacturer and will ensure the issue is addressed," the agency said. "Passengers should contact their airlines about specific flight cancellations or delays."

Southwest Airlines, which announced a large order of new MAX planes last month, said it removed from service a "subset" of its MAX fleet.

"While Southwest has not experienced any known operational challenges related to the issue, 30 of the airline's 58 737 MAX 8 aircraft are affected by the notification," the carrier said. "Southwest anticipates minimal disruption to our operation."

United Airlines, which also has ordered additional MAX planes since the jet was approved by regulators to resume service, said it is "voluntarily and temporarily removing 16" of its MAX planes from its schedule.

"We have been in touch with the FAA and Boeing and will continue to work closely with them to determine any additional steps that are needed to ensure these aircraft meet our rigorous safety standards and can return to service," United said. "We are working to swap out aircraft to minimize the impact to our customers."

American Airlines said it removed 17 aircraft "to complete necessary inspections and make any changes recommended or required by Boeing or the Federal Aviation Administration," a spokeswoman said.

All three US carriers still have MAX planes in their fleet not affected by the issue.

The 737 MAX has been a huge hit with airlines, and was Boeing's best-selling aircraft until it was grounded in March 2019 following the second of two crashes that together claimed 346 lives.

And after the Covid-19 crisis hammered the air transport sector, airlines cancelled hundreds of orders.

Investigators said a main cause of both crashes was a faulty flight handling system known as the Maneuvering Characteristics Augmentation System or MCAS.

Boeing continues to face litigation from families of victims who died in crashes on Lion Air and Ethiopian Airlines flights.

The FAA in mid-November cleared the MAX to return to service following upgrades to the plane and pilot training protocols. Other national regulators have followed suit since then.

Recent MAX orders by Southwest, Ryanair and others have underscored the appeal of the single-aisle MAX in the nascent airline industry recovery following the pandemic travel shutdown.

Aviation experts expect demand for domestic and short-flight service to recover before international flying.

Shares of Boeing fell 1.0 percent to $252.36.