Oh thats a great topic! Originally they included rotary and fixed wing assets (CAS and CAP) in their Kickstarter roadmap (how I love that term...), as seen here: https://imgur.com/a/HO1DZ and here https://www.kickstarter.com/projects/offworldindustries/squad/posts/1272444.
A little down the line OWI (the devs) scrapped plans for fixed wing aircraft due to concerns of 'muh realism' since maps are way to small to offer a beliveable experience with fast moving jets (I am paraphrasing here).
Since the game officially ended their early access phase and went 1.0 we can just hope that they will add CAS helis in as a free content patch, rather than a payed expansion. I don't want to sound entitled and do not request them to work on the implementation but interest in the game is pretty low for me at this state because the best aspects of PR - combined arms teamwork - is something Squad just can't do well.
I love the gunplay, the graphics and the sound engineering they worked on quite hard, but yet I am still drawn back to PR because in the end - for me - gameplay > graphics.
TLDR: The moment I can laze a Bradley on Yerkovia and a player controlled SU25 launches a laser guided missile on it I will be happy.