To connect two airports, simply drag your finger from the outbound airport to the destination airport on the map. As you drag the line, you’ll see an approximate cost for the route.
When you get close to the destination airport, you’ll feel a haptic feedback on your device. This means that you’re about to connect the two airports. If you’re happy with the route and the cost, just release your finger near the destination airport to connect them.
You’ll see a confirmation pop-up asking you to confirm the purchase of the route. If you change your mind, you can opt out of it.