On December 3, 2003, at approximately 0555 mountain standard time, a Swearingen SA227-AC, N340AE, and a Swearingen SA226-TC, N60U, both operated by Key Lime, Inc., were substantially damaged when they collided during night taxi at Denver International Airport, Denver, Colorado. Neither the airline transport pilot in N60U, nor the commercial pilot in N340AE, were injured. Night visual meteorological conditions prevailed. Instrument flight rules (IFR) flight plans had been filed for the non-scheduled domestic cargo flights being operated under the provisions of Title 14 CFR Part 135. Both flights were originating at the time of the accident. The pilot of N340AE reported that he had taxied north on taxiway Mike (M) to the "M10" intersection. There were several company aircraft in front of him in line for runway 17R. He came to a complete stop behind a Cessna 404, remaining partially on the M taxiway. The pilot of N60U reported that he was taxiing north on the M taxiway, en route to runway 8 for departure. He had seen the lights from an aircraft holding short of runway 17R; however, he did not see the lights of N340AE until it was too late. The pilot of N60U reported he applied full brakes and used reverse thrust but was unable to avoid hitting N340AE. Both airplanes were examined at the scene. N340AE, was turned to the right during the collision, entangling its empennage with N60U's empennage. The outer 8 feet of N60U's right wing was severed. The outboard 2 feet of the right propeller's blades showed chordwise scratches, torsional bends, and leading edge gouges and chips. The airplane's empennage was crushed and bent. The bottom empennage of N340AE was scraped and torn. The airplane's left wing tip was bent upward, and showed skin wrinkles. An 8-foot long, 2-foot wide section of the left outboard wing's trailing edge was torn out. The airplane's empennage was crushed and bent.