An elaborate "Subshuttle" subterranean rapid transit system was constructed during the 1970s, due to the vulnerability of air transportation to attack. The Subshuttles utilized a magnetic levitation rail system. They operated inside vactrain tunnels and ran at hundreds of miles per hour. The tunnel network was comprehensive enough to cover the entire globe. The PAX organization inherited the still-working system and used it to dispatch their teams of troubleshooters.