A Delta flight headed to Seoul, South Korea, had to dump fuel and return to Detroit Metropolitan Airport on Saturday after a light in the cockpit indicated there possibly was an open maintenance panel on the outside of the aircraft, a spokesman for the airline said. Flight 159 took off from Detroit at 4:48 p.m. ET, and about 30 minutes later the indicator light came on, Delta spokesman Trebor Banstetter said. The plane, which had 375 passengers on board, circled Lake Michigan, dumping fuel for about an hour in order to help ensure a safe landing, which it did shortly before 7 p.m.