On HP domestic flights, they do not check id at the gate nor do they refer to pax by their names.

On all international flights, ids are checked at the gate, so you would have to go femme once you are inside the plane (ie change in the toilets). I now understand the thrust of you query. How would an airline react to a male pax who boarded as a male and changed persona mid-flight.

On Far Eastern airlines and certain europeans ones, where they refer to you by name; i.e. Mr X or Ms Y, they maybe confused at the start, I see.

Personally, I do not see this as an airline issue but how worldly the cabin crew are. Given that many FA are "family" or friends of the family, then they may be non-plussed. However, some of the younger crew might be.

Perhaps and FA might care to comment if such issues are covered in their training of how to hand difficult circumstances. I suspect is might not be on the curiculum so you are back to worldliness of the crew or the Flight Manager.