Self employed?
How instructors are contracted is very very different one from another.
A CFI working full time and receiving a wage or salary and also an instructor in a similar circumstance is obviously employed. However many are not; working ad hoc and being paid ad hoc.
I do not pay part time Instructors a retainer but do pay travelling/turn up out of pocket expenses when appropiate. They are paid by the 'hour flown' or part thereof. Weather will in the most part determin how many hours if any that are flown each day. The Instructor alone determines the appropiate lesson for the student and the content to be flown that day and also whether the met conditions will allow the lesson aim to be achieved - in that sense and in others they retain a professional independance. I would of course expect all Instructors to work in consultation with me in providing continuity and policy.
Taxing and NIC would be a nightmare in the circumstances for ourselves and the Revenue because pay and benefits would be unpredictable and difficult to manage and audit. Which is why, I believe, the Revenue continue to accept the 'self employed' status, in the main, of part time Instructors.