As far as UK law is concerned.
Just because you claim to be self employed doesn't mean HMRC consider you are.
The moment you start using Ltd companies or self employed status to gain tax benefits you may be audited (unlikely) to prove your actual self employed status.
IR35 is a real grey area, but you need to show the inland revenue that you are a freelance contractor providing services to another company rather than a disguised employee.
If HMRC decides you are a "disguised employee" rather than truly self employed that is when HMRC will come after you for any falsely claimed tax benefit or unpaid tax due, on top they will charge interest and also any subsequent court fees you could be liable for.
Electriclightfoot, if this is your first commercial job then afraid to say HMRC would see you setting up a limited company then attempting to claim tax benefits as blatant disguised employment and is viewed as an attempt at dodging tax.
If you have previous experience working as a commercial pilot then you have a viable case for starting a limited company that offers piloting services.