The MAX update, issued via a news release Friday, is short. 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, reads the first portion. The company goes on to say the issue is related to electrical grounding and that it is working with the Federal Aviation Administration.

A Boeing spokesman told Barron’s the issue was discovered in production and that the company is in contact with all affected airlines. Boeing will provide more information as it becomes available.

The problem might seem small, but any MAX news is likely to generate a stock- price reaction. The MAX was grounded worldwide for almost two years—between March 2019 and December 2020—following two deadly crashes inside of five months. The company spent months fixing flight-control software and testing fixes.

The MAX’s return in December has helped the stock. Boeing shares are up about 50% over the past six months, partly because the rollout of vaccines for Covid-19 has raised hope that demand to travel, and thus for jets, will pick up.

Commercial air travel was decimated by the global pandemic, but people are slowly returning to the skies. Over the past week, about 10 million people flew commercially in the U.S. That is down about 38% compared with 2019 levels, but up almost 1,200% compared with 2020.

Write to Al Root at allen.root@dowjones.com