Firstly, the US launches over the ocean. Some other countries can’t / don’t bother, and often drop bits of rockets near people which is generally considered a bit rude.

Secondly, there is an exclusion zone underneath the rocket’s flight path and they won’t launch if they pick up a ship or plane in that zone. Governments publish that exclusion zone through specific channels - Notice to Airmen, and Notice to Mariners - with warnings to steer clear of the area at specific times.

Pilots and ship’s captains should check for notices before heading out - for commercial operators this is part of their everyday checklist.