[dingaling]

> Why is it that we can track boats with satellites but not planes?

Satellites don't track either ships or aircraft, except for huge nuclear-powered RORSATs that watch the fleets of rival superpowers.

However whilst many trans-oceanic aircraft do have VHF / UHF datalink uplinks through the Inmarsat satellite network the majority use line-of-sight UHF transponders ( beacon-tracking ) to supplement radar ( skin-tracking ):

https://fr24.com/2016-05-19/00:28/12x/MSR804/9c0b766

Transponder interrogation is often referred to as "secondary radar" but that's a misnomer that unfortunately took hold in the industry. It relies on 'squitting' a generated response, not on reflections from the aircraft structure.