Originally Posted by
Desdinova
I had figured it was to do with the timing of fare filings and availabilities. That is, ITA was finding fares the booking sites either no longer had or had not yet received.
I've seen the same thing so this is part of the issue at least. But I am seeing a lot of these discrepencies. My perception is that matrix searches are running out of gas more quickly than they use to - i.e., the failure rate at retreiving the lowest fares goes up more quickly as one increases the scope of a fare search.