United Air Lines Flight 4

United Air Lines Flight 4 was a Boeing 247D, registration NC-13317, operating on a scheduled flight from Salt Lake City, Utah, to Cheyenne, Wyoming, on October 7, 1935. The aircraft last contacted Cheyenne at 02:16 or 02:17 local time, reporting its position as Silver Crown beacon. Cheyenne called the flight at 02:21, and no further communications were received from the accident aircraft. At 2:00 a.m. the weather at the Cheyenne airport was recorded as clear with ceiling unlimited, air temperature of 41.7F (5.4C), and dew point 37.0F (2.8C), and winds out of the northwest at 9 miles per hour (14.4 km/h).

The wreckage was located 3 mi (4.8 km) east of Silver Crown, and 7.4 mi (12 km) northwest of the Cheyenne airport, at an elevation of 6,553 ft (1997 m). Note that the elevation of the crash site is only 370 ft (113  m) higher than the airport elevation. The aircraft struck the ground in a shallow descent just below a small knoll. Marks on the ground made by the propellers, fuselage, and engine showed the aircraft was in a normal flight attitude. Propeller marks and engine damage established the engines were developing normal power and the aircraft was at cruising speed. An untouched knoll 60 ft (18 m) further back on the flight path and 3 ft (0.9 m) higher established that the aircraft was descending. The accident claimed all souls aboard, which included 9 passengers and three flight crew.

The captain of this flight was highly experienced and familiar with the topography and unique features of the approach environment. Possible factors include darkness, sleep deprivation (captain), fog (speculative). The probable cause was determined to be pilot error in failing to monitor altitude or location. The actual accident report is available through the link below.