This Is The US Air Force's,

latest toy,

it is a Maglev (derived from magnetic levitation) a transport method that uses magnetic levitation to move vehicles without touching the ground, with maglev, a vehicle travels along a guideway using magnets to create both lift and propulsion, thereby reducing friction by a great extent and allowing very high speeds,

the highest speed recorded so far for a Maglev was 603km/h 373 mph, but the US Air Force has broken that record, although to be fair it was not a commercial train, the tests took place at Holloman Air Force Base, located in southern New Mexico near White Sands Missile Range, the sled, levitated by magnets, set two speed records in early March, first, the sled reached a top speed of 513 mph, beating the sled’s previous record of 510 mph, then, two days later, the sled accelerated to 633 mph down the 2,100 foot track, the fastest speed recorded for the configuration so far, 

so why is the Air Force making a sled go this fast? Partly just for the science of it, and partly as a test bed for future vehicles or weapons, like hypersonic missiles.