Why don't aeroplanes have some sort of sonar?
If bats can do this, why aren't aeroplanes equipped with the same sort of things?
Aeroplanes are, but just not at those frequencies. They use other types of techniques such as radio waves for finding direction, landing and other components. Bats are not equipped with radio receivers, but they are equipped with sound receivers and they use those instead. Submarines use sonar, which is the same sort of thing. They borrowed that from bats and dolphins.