[dsjoerg]

There's lots of water near NYC and SF so maybe you do your sonic boom over the water and then turn towards land?

[itp]

That's not how a sonic boom works. A sonic boom doesn't occur just at the moment that an object exceeds the speed of sound; it's a continuous phenomenon that is experienced by a stationary observer as a momentary event.

https://en.m.wikipedia.org/wiki/Sonic_boom

[hamandcheese]

The sonic boom is continuous at speeds above Mach 1