A plane undergoing maintenance work left a taxiway and went down an embankment at Hartsfield-Jackson International Airport in Atlanta Tuesday, officials said. Delta Air Lines spokesman Eric Torbenson said mechanics were testing the Boeing 737-700\'s engines when they \"experienced a problem with the plane\'s braking system,\" The Atlanta Journal-Constitution reported. Only the two mechanics were on board the plane, Torbenson said. They were not injured. The incident prompted a closure of the taxiway, but the Federal Aviation Administration said no flights were delayed.