I wish, Aws have new game play for alliance member. When i joint to alliance, i can share code with them.
Exam: my base is VVTS. I open route VVTS to Samporo RJCC transit at Taipe RCTP. With first flight VVTS-RCTP operated by VJ Airline (me), and second flight RCTP-RJCC operared by Taipe airline (a member of my alliance).
It's a nice idea. Due to game world rules that two airlines from the same alliance cannot saturate a route, most alliances make a rule that only one airline can fly it, usually the one who's HQ it is.
Why not display this route as a "code share" on the airline route map of the airline who has forfeited the route. Perhaps in a different colour. It wouldn't affect money or passenger numbers but would be nice eye candy for people who want to show all their destinations on the route map (even though they have given up this one to help their alliance mate).