14 CFR §437.59

1. (a)A permittee must conduct any key flight-safety event so that the reusable suborbital vehicle's instantaneous impact point, including its expected dispersion, is over an unpopulated or sparsely populated area. At a minimum, a key flight-safety event includes:
   1. (1)Ignition of any primary rocket engine,
   2. (2)Any staging event, or
   3. (3)Any envelope expansion.
2. (b)A permittee must conduct each reusable suborbital vehicle flight so that the reentry impact point does not loiter over a populated area.