A small, commercial airplane crashed into a building early this morning, causing a fiery explosion and killing the pilot, officials said. No one on the ground was injured. The FAA operations center identified the plane as Alpine Air flight No. 5008. Alpine Air confirmed the plane was carrying mail bound for Great Falls and Havre. Postal Service employees were at the scene, trying to gather whatever mail remained of the just over 4,000 pounds loaded on the plane, said spokesman Al DeSarro in Denver. "It looks like a good bit of it was destroyed," he said. "We're going to do our best to try to salvage, recover as much of it as we can." Postal Service spokeswoman Lisa Bloomquist said postal workers were gathering mail that was scattered in a wide area around the site of the crash, some as much as two miles away. The plane had just taken off from Billings Logan International Airport when it crashed into a construction materials building at 1:25 a.m., Federal Aviation Administration spokesman Mike Fergus said. "I just watched the light come out of the sky," witness Mike Krause told The Billings Gazette. "To me it looked like the plane was upside down. And then it just came straight down into the lot." The plane appeared to hit the ground in the lot of a rental business and skid into the construction materials building, witnesses said. Duane Demars, who lives nearby, said he heard two loud explosions and four smaller ones. "It sounded excruciating," he said. "When I got here, flames were at a length of 200 to 300 feet and 20 feet high in the air." The construction materials bui lding and plane were destroyed by the blaze, and a nearby United Rentals Highway Technologies building was damaged by debris, Fergus said. The Billings Fire Department confirmed the pilot's body was found in the wreckage. His name hasn't been released. Airport fire chief Michael Glancy said at least 300 gallons of jet fuel spilled in the crash, creating puddles that caught fire. According to Alpine Air's Web site, the company has a fleet of 29 airplanes and its biggest client is the U.S. Postal Service. The company is headquartered in Provo, Utah.