To me it makes sense that the FBI needs a fleet of surveillance planes for investigations. It also makes sense that these aircraft carry civilian livery to be low-profile (same idea as an unmarked pursuit car).

What seems f-ked up are the shell companies. Why not come out and say "we have surveillance planes; we need them for investigations; here's how much money we've allocated in our budget to operate them."

The FBI shouldn't need to hide this.