Let's be clear from the start: Airfares are volatile.
I know this as founder of Airfarewatchdog.com, which seeks out low fares. And I also know this as someone who travels for pleasure.
So although it's generally true that flying on a Tuesday or Wednesday is cheaper than on a Friday or Sunday, there is no magic time of day, day of week or month of year to book a low airfare.
Airfares can change in a heartbeat, high one minute, low the next, and the trick is to buy when a fare on your route becomes a bargain.
First, sign up for price-drop alerts. Many websites offer these for free, distributing lists of unusually cheap fares, some of them "fat-finger" mistakes — in other words, operator error.
These bargains usually expire quickly, sometimes in a matter of hours. (The late airfare guru Tom Parsons used to call these "snooze-and-you-lose" fares.)
When you see a great deal, buy it and think later. You almost always can change your mind and cancel within 24 hours, per U.S. Department of Transportation regulations.
Here’s what I use
The Explore site allows you to choose a trip length, departure city and an arrival city or region (such as United States, Europe or Boston), then displays a selection of the lowest fares available for the next few months. It's ideal for anyone with flexible travel dates and destinations.
The Flights site asks you to choose your origin city and destination along with specific travel dates so it's geared more to those who have less flexibility.
None of these sites includes Southwest Airlines, so you also need to compare at Southwest.com. If you're date-flexible, use Southwest's low-fare calendar option.
Don’t forget OTAs
They also sell air-plus-hotel packages that usually cost less than buying separately, and they sometimes have fares that are much lower than the same flights and dates sold directly by the airline sites.
Make sure the site covers your carrier
Be careful with basic economy
On domestic routes, those fares typically cost $40 to $60 less round-trip than regular economy, although the savings can be greater to international destinations.
Buy one of these fares and, except on Delta, you'll pay even for a carry-on bag unless it's small enough to fit under the seat in front of you. You won't be able to choose a specific seat before check-in (which means you'll end up in a dreaded middle seat) and your fare will be nonrefundable and nonchangeable.
Although I would never buy one of these airfares, my millennial friends, who apparently travel with just a change of clothes and a toothbrush stuffed in a backpack that slides under the seat, tell me that they're worth the inconvenience.
George Hobica is the founder of Airfarewatchdog.