Airbus A320United Airlines

evacuation of the aircraft due to reported, but unverified, aircraft condition and poor communication between Aircraft Rescue and Firefighting personnel and the flight crew.

The air traffic controller's failure to ensure the runway surface area was clear of vehicles before clearing an aircraft for takeoff. Also causal was the flight crew's decision to initiate a takeoff while the Runway Status Lights (RWSL) Takeoff Hold Lights (THLs) were activated. Contributing to the incident was the lack of a standard procedure for vehicle operators to request runway clearances and resultant "hear back/read back" error between the vehicle operator and the air traffic controller.

The flight crew's continued flight into a closing gap between areas of thunderstorm activity and their failure to maintain the required lateral separation from the thunderstorms, which resulted in the airplane's encounter with hail and subsequent airplane damage. Contributing to the incident were the company flight dispatcher's failure to provide complete and timely weather information to the flight crew and the Denver air route traffic controller's failure to provide significant pilot weather report information…

The approach controller's delayed transfer of communications on the A319 to the tower controller and failure to account for the aircraft's speed when he directed the crew to turn north. Contributing to the incident was the 747 crew's transfer of radio communications to departure control prior to being directed to do so by the tower controller.

The company tug operator's failure to maintain clearance with another aircraft during the pushback process. Also causal was the ground controller's failure to alert the pilot of the other aircraft and tug operator of this airplane of the simultaneous pushback occurring from adjacent gates. Contributing to the accident was the company's pushback operation without the use of wing/tail walkers.