Ah-ha
Thanks Mia, that would explain why (when I went back to the MR Rewards site after christianj's advice) the Airline Redemption Option disappeared altogether from my account - strange, since I've had the card for 7 years. One would think that if this major overhaul in the program were going to happen, American Express would explain that the Blue Card is now veritably useless. Evidently it's time to get one of the traditional cards.