The U.S. Air Force is starting to research the environmental impact of proposed changes to flight training areas in rural Arizona. 

The study will consider places that allow military aircraft to fly at lower altitudes and practice later at night for training.

The alternatives could change flight restrictions in areas northwest of Phoenix, southwest of Tucson, and in eastern Arizona extending into New Mexico. 

The training areas are used for aircraft from Luke and Davis-Monthan Air Force Bases and the Morris Air National Guard Base. 

Along with lower flight paths, the Air Force could release flares at lower altitudes and allow for supersonic flights in half of the areas.