From S.Dakota to Wyoming.
Below:
an explanation of "why"
with a map at link.
and an interesting tidbit about setting off falling flares
( why, what could go wrong with flares and dry conditions ??)
"The Air Force’s existing training areas, developed during the Cold War, are too small and flat to prepare pilots for the war in Afghanistan where planes and weapons now have longer ranges and reach higher altitudes than decades ago. To bring training up to speed with modern aircraft and warfare technology, two Western Air Force bases—Ellsworth in South Dakota and Cannon in New Mexico—are seeking public input on expansions of their training areas"
"The planes would drop chaff -- very fine strands of silica coated with aluminum that create a cloud-like decoy to hide planes from radar -- and lit flares that would burn out before they reach the ground. In addition, though not currently planned, the Air Force would reserve the option for up to 20 aircraft to fly together in special exercises on up to 10 days per year, some reaching supersonic flight, which causes a loud sonic boom, at heights of 10,000 or more feet."
http://www.hcn.org/blogs/goat/whos-terrorizing-who-1