For android based earlier it used to give three options while renewing.
Monthly
Half yearly
Yearly.
Now it shows only monthly which is not fair. Even if many people are subscribing for one month( as per infinite flight), there should be half yearly and yearly subscription option while renewing.
Cameron (who is an Infinite Flight staff member) stated that this was to simplify the subscription model as the 1 month option was the most popular between users. Cameron also stated that having multiple subscription options requires more maintenance then having the one option.
If you are currently subscribed to the 6 month or 1 year subscription through your respective app store and you have auto-renew enabled you will be able to renew on your current subscription plan.