Originally Posted by
FlyerWx
I'm taking an educated guess based on what DL does, but the reason the fare basis doesn't start with B is because Basic Economy fares have different "underlying" fares. For example, the first letter in your example is an O, so it is an underlying O fare with the basic economy restriction.
Basic economy fares are filed using the B booking inventory code and require dual availability (book B but another applicable main cabin inventory must also be available)
So, instead of a Y-UP, this is a B-DOWN? Hmm. If a flight is cancelled, can we then try to claim a refund based on the underlying regular main cabin fare??? What goes around comes around!