[MortMan]

Accelerating and decelerating will kill passengers, especially given the short distances (for 700mph) being traveled.

Also, the sound barrier will be shattered endlessly, which I doubt will please the neighbors.

[USFRIENDINVICTORIA]

If it accelerated at the same rate as (say) a Corvette, it would reach 700 MPH in under 30 seconds. About 6 miles would be required for both acceleration and deceleration.

The idea is to keep it below the speed of sound (775 mph at ordinary pressures, less in a partial vacuum). There are plenty of reasons this tech might never work -- those (acceleration and deceleration) aren't among them.