Q. I had a terrible situation last week: My husband needed to go to Dayton for business. (We're  in California.) We had fewer than seven days in advance to book and I was trying to book on a Wednesday. All flights on Expedia, Travelocity, Orbitz, and even on carrier's direct Web sites (Delta, Southwest) were giving me air fares of over $600 round trip! I was at a loss. I did find one that he would have taken (I think it was around $564 round-trip including tax, but it went to $800 as I was booking it).  I showed him the results on the Web so he saw the fares and options. So the next morning, my husband asked an assistant at his Dayton office to look into it. As it turned out, she got the same flights I looked at but for just $387 round trip!  

This is not the first time that I have had fares go up as I'm researching. Of course, I know that fares fluctuate constantly, but this seems to happen to me all the time. Is it possible that our computers somehow get "cookies" or some linkage that tracks our booking research and jack up the prices. The gal in Dayton also said that she had heard that somehow, fares are higher for people booking in California versus the Midwest. What can I do as I'm losing faith in the travel Web sites and I'm losing credibility in the eyes of those that I book travel for. Does this happen to anyone else?

A. Sometimes there is just one seat available at the lowest fare on a particular flight and since hundreds of thousands of people are searching fares in any given week, it's possible that between the time you saw the low fare and the time you attempted to book it, someone else had grabbed it. Airlines also change fares faster than ever before thanks to "improved" technology. And certainly over the course of a day of from one day to the next, a fare can change dramatically. That's why we urge people to sign up for free fare alerts by email and Twitter. Do "cookies" play a part? It's possible. Our fare researchers at airfarewatchdog.com have noticed that if they research a flight on a particular route and don't book it, but then come back a few minutes later the lower fare disappears unless they clear cookies on their browser. It doesn't happen often, but we have seen this. Is this because the booking engine showed the lowest fare and it wasn't booked so to save time it then showed the next highest fare? We don't know. But it doesn't hurt to clear cookies from time to time.