The crew declared an emergency after taking off from Orlando International Airport on Tuesday and returned to the airport safely.
No passengers were on board as the aircraft was being ferried to Victorville, California, where Southwest is storing the aeroplane because of a nationwide commercial flight ban.
The 737 Max was grounded in the United States on March 13 after a deadly crash involving a Max in Ethiopia on March 10. It was the second fatal crash involving the plane model in the past five months.
US airlines are allowed to shuttle the planes but cannot carry passengers.
The FAA said it’s investigating but the emergency was not related to anti-stall software that is suspected as a cause of the two fatal crashes, including one last year involving a plane from Indonesia.
Airport spokeswoman Carolyn Fennell said one of the airport’s three runways was shut down for cleaning after the landing. She said it was standard procedure to check a runway for debris after an emergency landing. It wasn’t clear if any parts actually fell off the plane.
Southwest said the plane’s pilots reported a “performance issue” with an engine shortly after taking off for the California airport, where it was flying to be in short-term storage. The Max 8 jet was to be moved to Southwest’s Orlando maintenance facility to be checked, a company statement said.
An Ethiopian Airlines Boeing 737 MAX 8 went down minutes into a flight from Addis Ababa to Nairobi, Kenya, killing all 157 people on board earlier this month.
The Ethiopian tragedy came after a Lion Air jet of the same model crashed in Indonesia in October 2018, killing all 189 people on board.
Tuesday’s development comes as the American manufacturer Boeing struggles to cope with the fallout from the two crashes, which have cast a spotlight on the safety certification process and shaken confidence in a plane that is crucial to its future plans.
The Boeing 737 Max is the fastest-selling aircraft in the company’s history with roughly 370 delivered so far and some 4,700 more on order.
Some airlines have said they are reevaluating existing orders of the 737 Max in the wake of the deadly crashes.