The plane maker said it was "working closely" with the US Federal Aviation Administration (FAA) and would direct clients on how to resolve the issue.
US aircraft manufacturer Boeing has said it recommended that 16 clients flying its 737 MAX models address a "potential electrical issue," a new setback for its most popular plane.
"Boeing has recommended to 16 customers that they address a potential electrical issue in a specific group of 737 MAX airplanes prior to further operations," the company said in a statement on Friday.
Boeing managed to get the 737 MAX back into the air 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 potential problem identified on Friday requires "verification that a sufficient ground path exists for a component of the electrical power system," the statement said.
READ MORE: Boeing 737 MAX given go ahead to fly again
Electrical systems must be grounded to avoid overloads that can cause serious failures.
Boeing did not say which airlines were concerned nor did it give the number of aircraft involved.
The plane maker did say it was "working closely" with the US Federal Aviation Administration (FAA) and would direct clients on how to resolve 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.
Around 450 of the planes have been delivered to date to 49 airlines or aircraft leasing companies.
Crashes mar reputation
After the Covid-19 crisis hammered the air transport sector, airlines cancelled hundreds of orders.
Boeing currently has more than 400 aircraft waiting to be delivered to clients, and does not expect to eliminate that stock until sometime next year.
The MAX was grounded after 346 people died in two crashes – the 2018 Lion Air disaster in Indonesia and an Ethiopian Airlines crash the following year.
Investigators said a main cause of both crashes was a faulty flight handling system known as the Maneuvering Characteristics Augmentation System, or MCAS.
The FAA in mid-November cleared the MAX to return to service following upgrades to the plane and pilot training protocols. Other regulators have followed suit since then.
Commercial flights resumed in December 2020 with Brazilian airline Gol, then in the US and Canada. It is still grounded in China.
On March 29, US carrier Southwest Airlines said it had agreed to buy 100 more Boeing 737 MAX planes, providing a key vote of confidence.
Other significant orders had already been announced by Ryanair, United Airlines and investment firm 777 Partners.
Airline sector looks to rebound
The Southwest order, which includes options on another 155 new MAX planes, is the biggest for the model since regulators cleared it to resume service.
Major airlines continue to burn through cash due to low travel volumes caused by the Covid-19 pandemic, but the sector expects to rebound this year.
Meanwhile, Boeing continues to face litigation from families of victims who died in crashes on Lion Air and Ethiopian Airlines flights.
In January, Boeing agreed to pay $2.5 billion in fines to settle a criminal probe with the US Department of Justice over claims the company defrauded regulators overseeing the 737 MAX.
The industrial catastrophe has cost Boeing billions of dollars and seriously damaged its reputation.