Originally Posted by RobOnLI
Good catch on the IP addresses being the same for the two URL's (res.nwa.com and flynwa.expedia.com). Still doesn't explain why one can show me BRU-SEA availability and the other one cannot.
-RM
This is only my hunch.
Each search is set to take maximum of X seconds. If no fare is found within this X seconds than you get no availability message. Simply, the search expired.
I think it has something to do with the load on the server. The higher load the longer the search query takes. The more complex fare (like 3 leg vs 2 leg) the higher chance you get the "no availability" message, if the server is under high load.
This is the same "no availability" message one gets when there is truly no availability between the given city pair.
An analogy could be found in google.com. When google.com is under high load they do not search the whole index. They search only a part of it.