According to the Federal Aviation Administration's notification, 300 Boeing 777s used by United and American Airlines are at risk of exploding fuel tanks.

Earlier this year, the FAA recommended a new airworthiness directive to address a possible defect in Boeing aircraft.

The problem, according to the FAA proposal, was an electrical malfunction on the company's 777 aircraft that, if ignored, might result in the fuel tanks on the planes' wings catching fire and blowing up.

According...