Do I have to check in my walker or is it carry on?
Carry-on. The airline attendant will store it for you once you are seated.
I can’t say what the airlines will do for a walker. But we have brought on board a 3-legged cane that unfolds into a little seat. Flight attendants put it in the closet and we pick it up on our way out of the plane.
When I last flew they checked my Walker for me in. Then they put me in one of their courtesy Wheelchairs and had somebody wheelchair me over to the terminal area that I would be flying out of. Then when it came time to board the plane was able to board the plane before anybody else because of being disabled and they will cheered me right up to the seat. When got off the plane they had a wheelchair there for me and took me down to baggage claim where I got my Walker in my other baggage and it took me outside to wait for my ride. This was at Ontario International Airport in Ontario California.