Does anyone else hear what sounds like a LARGE formation of air force planes going overhead late at night (2 am, 3 am, 4 am)?

I keep hearing what sounds like major plane formations go overhead late at night. I live on the outskirts of Louisville in north central Kentucky.

The army base Fort Knox is about 40 minutes to my south southwest. I can often hear them practicing with the big guns on weekday evenings and weekend afternoons.

The air traffc late at night only recently "picked up", say around mid to late March 2010. Now I hear a low roar and a vibrational feeling at least a few times each evening overnight.

Could it be our air force shuttling planes and or supplies to help with the fighting that's occuring on the U.S. side of the U.S.-Mexican border? Are TPTB having to mount a much larger offensive along the border to stave off the sheer numbers of illega;s that are making a last ditch effort to cross into America?