Loyalty: Flair does not have a loyalty program.
Booking: In the title field, only Mr, Mrs, and Ms are listed. Flair uses the title field to fill the gender field when collecting passport data; the gender field cannot be changed on its own.
Check-in: I have not yet attempted check-in with a gender X passport on Flair.
Company response: I have not yet contacted Flair about this.
Let Me X Plane 