According to the NTSB, the probable cause of the crash was "the pilot's inadvertent encounter with instrument meteorological conditions and subsequent failure to maintain terrain clearance."

[2] An FAA representative stated the helicopter was being operated under visual flight rules and was not being handled by air traffic control, a practice he called "perfectly normal.

The first fire department responders to the accident site reported that the area was covered by intermittent waves of fog, which made locating the wreckage difficult.

The accident site was located on mountainous terrain on a 45° slope at an elevation of 4,000 to 4,300 ft (1,200 to 1,300 m) above mean sea level,[2] below a large electrical transmission tower,[1] a little more than a mile east of I-15, and north of Highway 138.

[1] The first identified point of impact, a ground scar located next to the separated tail boom and the left skid, was near the base of the mountainous terrain, with the debris path emanating upslope.

On September 7, 2002, three crew members died when a Mercy Air helicopter based in Nevada crashed in Nipton, California after the main rotor blades separated while maneuvering in flight after dark.

[10] Three out of four of those accidents, though, occurred when no patient was on board the aircraft—a fact aviation lawyer and helicopter pilot Justin Green said is attributed to lax regulations by the FAA.

The NTSB had previously recommended that the FAA require all operations to be conducted under the more restrictive Part 135 regulations whenever medical personnel are on board.

[13] At the time of this accident, Mercy Air was San Bernardino County's only private, permitted helicopter ambulance service provider.

[1] An estimated 3,000 people, mostly uniformed nurses, medics and firefighters, attended a three-hour memorial for the flight crew a week after the accident.

[15] This accident also led to increased efforts to establish a trauma center in the high desert region of San Bernardino and Los Angeles counties.