SALT LAKE CITY (AP) — An air tanker dropping retardant on a southern Utah wildfire earlier this month veered off its flight path while following a lead plane moments before crashing into mountainous terrain, killing both pilots aboard, according to a preliminary federal report on the accident.

The National Transportation Safety Board found the Lockheed P2V-7 was on its second flight of the day dropping retardant when it followed another plane into a shallow valley less than a half-mile wide and 350 feet deep.