Loyalty: In addition to Male and Female, Air Canada includes “Undisclosed” as a gender option on Aeroplan profiles.
Booking: Air Canada includes “Undisclosed” in the gender field when booking a flight.
Check-in: Online check-in includes “Undisclosed” as a gender option. I also checked in using my gender X passport at a physical kiosk, and the passport was recognized successfully.
Let Me X Plane 