Fully agree that we'd need to know the methodology. This paragraph seems to sum it up, though clearly more detail would be needed:

"IdeaWorks made 6,160 booking queries at the websites of 22 frequent flier programs during February and March 2010. Travel dates spanned June through October 2010; 10 long-haul routes and 10 city pairs under 2,500 miles were checked to assess reward seat availability."

Here's the link for the press release from the company that conducted the study:

http://www.ideaworkscompany.com/pres...ailability.pdf

Like chemist661, I'm also surprised that UA ranks higher than AA, even given that it seems like the methodology excluded the ability to get award flights on partner airlines (and therefore didn't take Starnet blocking into account). Could be a product of specific routes that were checked or other aspects of the methodology. Also, I believe that AA does save more award inventory for EXPs, which could skew the experience of some of us here.

Delta results no surprise. From what I've read about the US program here, I'm surprised by how low it ranks, though maybe the more favorable reports involve the availability of partner airline flights using US miles, as opposed to US flights themselves.