I was searching for weeks on several sites for a round trip to Italy, and had the same frustrating fluctuations. I searched multiple sites,and flight combos, and recorded the results (I'm a bit compulsive at times...) In the course of a week, the price could change 4 or 5 times, and the price one day could be $400 more or less than the day before. Sometimes, it was a $1 difference. Really? What pricing model are they running that tells them to change the price of a $1200 ticket by one dollar? Often, it was cheaper to have a one or two day layover in another European city than it was for a single trip that stopped in that same city. From my several weeks of daily searching, it seemed Tuesdays were the cheapest, and Thursdays the most expensive. I bought 4 months in advance, and it dropped a bit more for couple of weeks, and is now slightly higher. I found my fare on a search site, but bought direct from the airline as you often get better protection and notice on flight switches, and don't have to use an intermediary if there's a problem.