I wonder if the pilots volunteer for the run? It'd be interesting to know the internal culture with regards to it.
Edit - also the call is made continuously. They can back out any time.
https://en.wikipedia.org/wiki/Third-person_pronoun
Why create an account to make your initial comment? It doesn't seem very substantial or on-topic. The two reasons I can think of aren't very charitable, which is why I'm asking, assuming that it's neither of those.
To answer your question if you know the sex, you say the sex.
If not you use sexless pronouns like "their" and "they" even if they are not 'proper' by old strict standards, basically they are, because language evolves.
They may or may not have volunteered for the flight, but they do get the final decision to go in or turn back once the airline OKs it.