Centurion

What airline award programs remain that offer only Low and High tier level awards where a high award gets you seat if they have one for sale? I am convinced all programs will migrate to multi tier awards like Delta where a high award uses an extreme amount of miles.

Examples. American Advantage has Aadvantage Anytime award and United has Standard and Saver awards.

sdsearch

What other US-based miles-based airlines are there? You've only left out US Airways (which is due to merge with AA anyway) and Alaska.

In case you don't know, many overseas airlines don't have Standard awards, only the equivalent of Saver awards. So even the list of airlines with two levels of awards is not that big; many in the world have just one level of award I think.

For the record, yes, there are multiple LCCs in the US which have revenue-related redemption levels only. But in those case, it's not three levels, it's essentially an infinite number of levels, since every time the paid fare changes (not counting certain kinds of sales at Southwest), the number of points needed for redemption changes.

Btw, for a couple years American has had an option (for elites only? I don't remember, it's rarely talked about) for "dynamic awards", which IME are often slightly below Standard Awards and much bigger than Saver Awards, which are somehow tied to paid fares. They're only available on a subset of flights, and you have to go to a special web page to even look them up. But like I said it's rarely talked about, and I figure it's rarely used. (And AA itself rarely mentions it, so it's not like it's their biggest promotional thing. It sounds like an experiment which didn't work out so well...)

benzemalyonnais

Flying blue has tiered awards

Savvy Traveler

SQ (Singapore Airlines) also uses a three-tiered award system. The top level makes Delta look downright reasonable, which is no easy feat.

nux

BA allows Gold members to book any seat any flight for 2x the standard award amount.

QF allows booking any seat with the points requirement related to the cash fare price.