It's not cheating. It's a slow Internet connection. Here's how it works:
You and an enemy plane are flying. You see them, turn, and begin firing. You, on your screen, register that you successfully struck them. For this to happen, the signal containing the bullet must travel from your phone, along your Internet connection, to the server that hosts the game. From there, the enemy's phone request the signal, and the server sends it along their connection, into their phone, and they receive the information that you shot them down. Their phone then sends the signal back to the server, along his Internet connection, to the server. The server then sends that information out to everyone's phone, along their own connection. Once that signal reaches you, that is when you see that you successfully shot them down.
Make sense?