I have two suggestions - others with more knowledge of AC and AE rules can confirm if they will work. Could you buy a flight pass? If you are travelling those routes consistently that may make sense and you may save money - and they book into Flex so 100% mileage. Secondly, if you wait long enough to book, all the Tango fares disappear and you will have to book Flex, but the cost per ticket will be higher.