"The problem these days is that the airspace is already 98% used"
Not really. Air corridors are heavily used but they account for less than 10% of the actual airspace available and things are setup that way because antiquated computer systems can't handle the complexity of myriad "best route" paths.
Sorting this was one of the (failed) objectives of the last great North American ATC rebuild.
Effectively, current ATC systems _increase_ the danger, because they push most traffic into geographically constrained areas for "convenience" reasons instead of letting it spread out.
It's another one of "those things" which could be allieviated for substantially less than the cost of bailing out a few banks and which would pay economic dividends in short order. However it's not sexy, which means that getting governmental approval to invest the necessary sums of money simply won't happen until the entire thing comes crashing down around our ears (and a crash investment means poor design choices).
Biting the hand that feeds IT
