For west-coast police agencies, helicopters fly primarily patrol missions (75 percent of operations). Other operations include narcotics interdiction, photo missions, and rescue flights. Many east-coast agencies use helicopters only for on-call missions, such as medical rescue at accident scenes. A McDonnell Douglass Model 500 E helicopter costs approximately $600,000, plus accessories such as high intensity spotlights, loudspeaker systems, and police radios. It will cost approximately $300 an hour to operate the aircraft. If a sworn officer is trained at departmental expense, the instruction costs are approximately $30 an hour, and few trainees pass flight exams with only the minimum hours required (150 hours of flight time). Helicopters are thus a significant expense for police agencies, but those who have them are convinced they cannot provide mandated public service and public safety without them.