If you are just burning fuel you follow a smooth track, if you are actively tracking signals, looking between buildings etc the flight pattern will be spastic as all hell to optimize your ability to see/track/listen..
You can shove all kinds of things into a plane not typically used for signals and intelligence, with the added bonus of it not looking like an AWACS or E3...
just write in the type in bing or something, will usually get you the wiki for it(not that wiki is the paramount of truth or anything.... but generally accurate about stuff like this)