A new update for Apple is coming shortly and the subscription system is different than Android.
Due to the cost of maintaining (and increasing) the number of servers and also to help for future development, the game will be subscription based. It will be hyper cheap: less than $2 per month.
This is the description that will be published by Apple:
========================================================
This is a subscription based game.
A free trial period is included which contains a practice level and one airplane until you hit rank 3.
Afterwards, an auto-renewing subscription is required to play. The following information pertains to the subscription:
- Subscription to Dogfight service. This service allows you to play unlimited multiplayer time during the subscription period. It also gives you access to additional missions, airplanes and gadgets available only to subscribers. New content such as maps and airplanes is added regularly to subscribers.
- The subscription is an auto-renewing subscription that will be charged to your iTunes Account at confirmation of purchase. You can choose between two subscription payment periods (Tier 2: $1.99 monthly payment) and (Tier 5: $4.99 quarterly payment).
- This is an automatically renewing subscription unless auto-renew is turned off at least 24-hours before the end of the current period.
- Your account will be charged for renewal withing 24-hours prior to the end of the current period.
- Your subscriptions may be managed and auto-renewal may be turned off by going to your Account Settings after purchase.
- No cancellation of the current subscription is allowed during the active subscription period.
- Any unused portion of the free trial period, if offered, will be forfeited when purchasing a subscription.
You can read our Privacy Policy and Terms of Use at
www.dogfightplay.com/index.php/forum/4-a...c-y-and-terms-of-use 
