Oct. 1--If you live in or near Rochester, you've certainly seen or heard medical helicopters flying overhead.

As of this week, crews have been responding to trauma scenes for a quarter of a century. The first emergency flight for Mayo One was sort of accidental. Mayo Clinic's first medical helicopter started with a week of introductory flights to regional hospitals.

While the helicopter was in Whitehall, Wis., Saint Marys Hospital in Rochester got a call from a doctor in need -- a patient might not survive a road trip from Oshkosh, Wis. to Rochester. Did Mayo have any suggestions? Mayo One had paramedics aboard, so the doctor requested a patient flight.

Mayo One is now part of Mayo Medical Transport. It's one of four helicopters serving a 200-mile radius from bases in Rochester, Eau Claire, Wis., and Mankato, Minn.

Key events during 25 years of service:

--1984 -- Mayo One sees 57 medical flights

--1985 -- Flights for a full year increase to 402

--1989 -- Mayo buys a new, $2.5 million state-of-the-art helicopter after five years in service.

--1994 -- Mayo One experiences a "hard landing" due to a mechanical problem. But there are no injuries.