Originally Posted by AeroWesty

This policy change could be compared to the draconian program devaluations that occurred in 1989(?) following the massive build-up of FF program members and mileage balances resulting from the triple miles promotions of 1988.

I believe almost every program split miles into what were essentially "old" and "new" miles (I think TWA was one exception—I don't see two balances on my old Aviator statements). Delta applied award redemptions from the new chart first using "new" miles, then against "old" miles if you didn't have enough "new" miles, except if you specifically made an "old" miles redemption.

(There are some threads here on FT from people asking about where to find the old award chart that may have more info, if anyone's interested in exact details about how that worked.)

I used up my "old" AA miles long ago, and DL converted my small remaining balance to SkyMiles a few years back. I believe a few people here claim to still hold AAdvantage miles from that era that never expire and may be used against the original AAdvantage award chart, if I recall the terms of the mileage split and those posts correctly.

If anything, that's our precedent against retroactive program changes that are detrimental, regardless of the several outs the program T&Cs set forth.