I get asked this question a lot and I’m not sure if I’m ever able to answer it correctly since airline fare pricing is fickle and you should never count on deals on a certain day.
However, that being said, one of the best deal I ever found was a Delta fire-sale on European flights, which came to $230 total round-trip, and that was on a Tuesday. In my unscientific experience, I’ve also noticed cheaper fares on Wednesdays.
By the way, I found the epic fare to Europe (which hundreds of people took advantage of) by setting a Travelocity FareWatcher Plus Alert for JFK-MAD. When the airline lowered the base fare below $300, I received an email. Normally they add so many taxes and fuel surcharges that it doesn’t make the fare that special, but this time the fare actually stayed at $230, which got my adrenaline pumping as I quickly pulled out my credit card and started booking! I recommend setting FareWatcher Plus (click on the My Travelocity tab on the home screen) alerts for any city pairs you travel so you can get in on a deal before the masses. Airlines usually only release a certain number of seats for fare sales, so they are usually gone by Thursday/Friday.
My experiences seem to coincide with Scott McCartney’s recent article on buying airfare in which he finds that fares are usually lower on Tuesday/Wednesday. This piece was pretty interesting and McCartney interviews some of the industry’s top fare experts for their opinion.
I also get asked about the best day to book award tickets. Unfortunately, even with my practice with redeeming millions of miles, I don’t think there is a specific day of the week that can be counted on over another. Airlines have become smarter about releasing award inventory, whereas back in the day, they’d release a bunch 11 months before a flight and then intermittently throughout the year. That can still happen, but the trend I’ve seen is for the airline to open up closer to departure when they have a better sense of their actual flight sales. Overall, buying airline tickets (whether revenue or award) is a cat and mouse game, but the better informed you are, the more value you can get out of the system.