Officials say a United flight with about 70 people on board made a safe emergency landing yesterday morning at Yampa Valley Regional Airport. Flight 4919 originated from Aspen and was headed to Denver when the pilots indicated there was a mechanical problem with the right engine and they chose to shut it down. Airport director Kevin Booth says the plane landed safely shortly after 10 in the morning. The runway was closed for about 20 minutes while the plane was towed away. Booth says the flight was diverted to Yampa Valley because of the mountainous terrain between Aspen and Denver.