A new airworthiness directive set to be published this week by the Federal Aviation Administration will require enhanced inspections and fixes to portions of an outside panel that helps protect the engines on Boeing’s 737 Max from lightning strikes.

The company first identified the issue in December and said it involved composite panels that sit atop the engine housing on planes that were manufactured between February 2018 and June 2019.

In the airworthiness directive, the FAA said the panels may not have the quality of “electrical bonding” needed to shield the underlying wiring from lightning strikes or high-intensity radiated fields. As a result, the planes’ engines could lose power in the event of a lightning strike.

“The FAA is proposing this AD because the agency evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design,” the document stated. That is part of the reason the agency said it was expanding its directive to include inspection of all Max jets, not only those built in the time period Boeing specified.

News of the issues with the composite panels was first reported by the Wall Street Journal.

The Max has been grounded since March, after 346 people died in two crashes.

This latest issue heightens concerns about quality control at Boeing’s plant in Renton, Wash., where the 737 Max is built. Last week, the company reported that it found debris in the gas tanks of some of the several hundred 737 Max jets that have been built but not yet delivered to customers. The company said it is handling the issue.

In December, a former manager at the plant told a congressional panel that pressure to increase production of the 737 Max had created a “factory in chaos.” Edward Pierson said he repeatedly voiced concerns about production problems but was ignored. Boeing said it looked into the manager’s concerns but did not think the issues he raised were related to the crashes.

The FAA estimated that the airworthiness directive would affect 128 of Boeing’s 737 Max jets.

Boeing said that it would provide operators with necessary parts and that the costs of the inspection and fixes will be covered under warranty. The company said it does not expect the issue to affect its mid-2020 timeline for returning the 737 Max to service.

The enhanced inspections of the composite panels add to several steps Boeing must take to win approval from the FAA for the troubled jetliner to resume service. Boeing has been working on software fixes to an automated flight control system, known as the Maneuvering Characteristics Augmentation System (MCAS), which was implicated in both crashes. It must also design new training for pilots who will fly the Max when it returns to service.