Carriers have grounded some Boeing 737 Max aircraft following a notification from Boeing of a potential electrical issue.

In a statement, Boeing said it had notified 16 customers of the issue, saying the carriers should “allow for verification that a sufficient ground path exists for a component of the electrical power system.” Reuters reported the issue affects about 90 aircraft in total, including 30 aircraft that Southwest Airlines removed from service on Friday. Southwest said it expects “minimal disruption” to its schedule. United Airlines, Alaska Airlines and American Airlines also have pulled some Max aircraft from their schedules.

Boeing said the repairs could take up to a few days to complete, according to Reuters.

The U.S. Federal Aviation Administration cleared Boeing Max aircraft to fly late last year after they were grounded for about 20 months to address issues related to two fatal crashes of the aircraft. The FAA in a statement said it will “ensure the [electrical] issue is addressed” and that passengers should check with their airlines about potential delays and cancellations.