The only thing I can come up with is space vs ground based navigation. Most old planes will not be equip with built in GPS (I admit I don't know what equipment these jets have) and only use VOR or ADF technology. VOR and ADF are both ground based radio navigation tools, so easily sabotaged by destroying a radio tower, meaning your planes lose navigation. GPS, though, is space based and a lot more difficult to disrupt. If I had to guess this is the reason... It's also a lot easier to preplan and map a GPS plan, as you don't need to worry about tuning VOR beacons and switching the nav source.