These 2 posts reek of ignorance. First of all, commercial airliners dont do 1000mph, thats over the speed of sound. Second, while GPS may take 30 seconds to get a lock (no idea if this is true), the GPS would undoubtedly be always online. Third, they will obviously have redundant backup hardware onboard that is also always active in case the primary and secondary fail. Not only that, but its not like aircraft will all of a sudden fly right next to eachother, there will clearly be an ample buffer , and the system will work in conjunction with the current RADAR system until it proves itself.