US aircraft manufacturer Boeing said Friday it has recommended that 16 clients flying some of its 737 MAX models address a "potential electrical issue", a new setback for its most popular plane. Boeing managed to get the 737 MAX back into the air in late 2020 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 Friday requires "verification that a sufficient ground path exists for a component of the electrical power system", a statement said. Boeing said 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 big hit with airlines, becoming Boeing's fastest-selling aircraft until its grounding in March 2019. After the Covid-19 crisis decimated demand, airlines cancelled hundreds of the orders. Commercial flights with the 737 MAX resumed in December 2020 with Brazilian airline Gol, then in the US and Canada. 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. On March 29, US carrier Southwest Airlines said it had agreed to buy 100 more Boeing 737 MAX planes, a key vote of confidence for the aircraft. Other significant orders had already been announced by Ryanair, United Airlines and investment firm 777 Partners. mra-wai/lth