After trying to book my brother's family to Europe on Monday, I do believe (at least) in the accuracy of the NW website and NW phone reservations in listing fares and individual seat inventory.

The fare for one person at the NWA website listed as $901. The fare for 4 people listed as $1192. I called reservations, and they said that this was because there were only 3 seats available at the $901 fare (no more Q availability FRA-DTW). I double-checked at NWA.com, and, indeed, if I pulled up THREE seats the fare was $901.

So asked them to book 3 seats at $901. Then I went back online--just trying to see if the inventory was off somehow, but indeed, after I had booked the 3 seats on the phone, there were NO $901 seats available any more (which I had hoped to snag for the 4th person). So I called back, and booked one more seat at the $1192 rate--thhough the agent told me that it wouldn't be ticketed till midnight the next day, and I could try back, because inventory changes constantly.

Later that night, the fare on NWA.com for one person was still $1192. Early the next morning, and at noon, it was still $1192. But at 2pm that afternoon the nwa.com website showed a seat available for $901, so I called nwa reservations, and she was able to snag that $901 seat and substitute it for the $1192 seat--so although the 4 people were in two records, and it took 36 hours till that last Q seat turned up, they all travelled at the good fare.

When I checked back just one more time, the $901 seat was indeed gone, and the fare for one person now listed at $1192. One (and only one) Q seat had INDEED popped up (just in time) and everything corroborated.

NOT ONLY did the nwa.com listing match perfectly what the NWA phone reservation told me--but I was also using ORBITZ at the same time to track the availability of these rates (along with onetravel and travelocity every now and then), and what I was finding at NWA matched the Q availability, or lack of it, PERFECTLY across all these sources.

I don't know about the accuracy of ITN, but I was pretty impressed with the consistency of these other inventory offerings--and REALLY happy that by checking in at just the right time I was able to save another $300 before the ticketing deadline!