SPOKANE, Wash. -

A United Airlines flight traveling from Chicago to Portland was forced to make an unscheduled landing at Spokane International Airport late Wednesday night.

The Boeing 757 made a fuel stop in Spokane after 11 p.m. and then took off heading for Portland. About 20 miles out of Spokane, however, the pilot of Flight 959 noticed there was some sort of problem involving the hydraulics system on the aircraft and turned back toward Spokane.

Emergency crews were on the field as a precautionary measure but the plane landed safely.

All the passengers are being re-booked on another flight that will take them to Portland.