National Transportation Safety Board
A pilot taking off from the Lancaster Airport at about 3:30 p.m. Sunday noticed an indicator light alerting him to a fuel leak and immediately turned around and landed, FAA spokesman Lynn Lunsford said.
Southwest Airlines says it has finished inspecting planes grounded since the weekend.
Federal records show cracks were found and repaired a year ago in the frame of the Southwest Airlines Boeing 737-300 that made an emergency landing at an Arizona military base after a hole was torn from the passenger cabin.
Friday was a rough day in the skies for both North Texas-based airlines. A Southwest Airlines jet had to divert in Arizona just hours after an American Airlines flight had to land in Ohio.
Investigators are looking into what caused a hole to rip open in the fuselage of an airline jet as it cruised at 31,000 feet, causing a loss of cabin air pressure and forcing the pilot to make an emergency landing.