TULSA — Air Methods Corp., a private company headquartered near Denver, has assumed full operation of Tulsa’s Life Flight air ambulance service. Air Methods has supplied the helicopters, pilots and aircraft maintenance to Saint Francis Hospital and St. John Medical Center. Now, the company will employ medical staff on board. Three air ambulances will be based in cities outside Tulsa to provide the service: in Keefton, Pryor and in a third undetermined location. The change is part of a trend toward a community based model that provides more efficient service, said Craig Yale, Air Methods’ vice president of corporate development. Air Methods also provides air ambulance service to OU Medical Center in Oklahoma City but does not employ the paramedics and nurses.