The National Transportation Safety Board (NTSB) has determined that the probable cause of a midair collision between two emergency medical service (EMS) helicopters last year was failure of both pilots to see and avoid the other helicopter on approach to a helipad.  Contributing to the accident were the failure of one of the pilots to follow arrival and noise abatement guidelines and the failure of the other pilot to follow communications guidelines. On June 29, 2008, two Bell 407 EMS helicopters, operated by Air Methods and Classic Helicopter Services, collided while approaching the Flagstaff Medical Center (FMC) helipad in Flagstaff, AZ.  All seven persons aboard the two helicopters, including two patients, were killed and both choppers were destroyed."This accident highlights the importance of adhering to the regulations and guidelines that are in place," said Acting Chairman Mark V. Rosenker.  "Had these pilots been more attentive and aware of their surroundings, and if communications would have been enhanced, this accident could have been prevented."