Anyone know if ExpertFlyer used the same method for finding availability, or a similar method that might end up being dropped? Flight availability is the only real need I have in any of these sites, and after finding flightstats, realized I didn't need to pay for it. But I'd gladly pay for it that's the only option and if I'm guaranteed it'll stay around.

I tried to use the ITA Matrix, but it basically only returns ticketable results, with prices. In many cases I don't care one bit if something is ticketable, because I'm only interesting in searching one segment at a time with a particular booking class to only see if there's availability. But often the airline does not sell that booking class on just that one segment, but only as a complete itinerary. Trying to search for a complete itinerary though, with various different dates for each segment is a supreme pain. That's what I loved about flightstats - it would simply show all the booking classes and availability, allowing me to find the dates I wanted, and then when done book the ticket with the airline or some online site.