Airport City: How do I add friends?

You can add friends and check your Friends list in the Neighbors menu. To open it, tap on the Sociality button (the one with 3 people in the bottom menu) and then press the other button with 3 people. You can add friends in the following ways:

1. To add a random player, open the first tab and press the confirmation button. When the invitation is sent, the chosen players go to the Waiting List (the second tab) until they accept your invitation.
2. To add a certain person, open the Add Friend tab and enter your friend’s code. You can redeem 5 codes a day.