Mechanical problems forced an American Airlines plane en route to China to dump thousands of pounds of fuel over Lake Michigan.

WMAQ-TV reports that the flight took off from Chicago’s O’Hare International Airport on Sunday night and returned safely to O’Hare about 90 minutes later. American Airlines spokesman Ed Martelle says the plane bound for Beijing had 249 passengers aboard.

Martelle says the flight had to dump 151,000 pounds of fuel because landing over weight would have created problems. He says the plane landed within weight limits but did blow a tire upon landing.

Martelle says dumping the fuel wouldn’t harm the lake. He says the process allows the fuel to evaporate before it reaches the lake’s surface.