Cell phones often have 4G connections but if they're on wifi or laptops on wifi, we could collect the IPs of all airports and present the travel mode by default

Cell phones often have 4G connections but if they're on wifi or laptops on wifi, we could collect the IPs of all airports and present the travel mode by default. Phones could use GPS to detect when their in/near airports and inject an X-Travel-Mode cookie into HTTP requests.