Finally, there's a scientific answer to that magic number of days before a flight when tickets are at their cheapest.

The answer? Are you ready? Are you reeeally ready?

Fifty-four days before takeoff is, on average, when domestic airline tickets are at their absolute lowest price. And if you don't hit 54 days on the head, you should usually book between 104 to 29 days before your trip - within the "prime booking window" - for the lowest possible prices. In this window, ticket prices typically hover within $10 USD of the lowest price they'll ever reach.

At least that's what the data from 2013 tells us.

The folks at CheapAir spent the last year analyzing over four million airline trips. They tracked ticket prices from 320 days before takeoff all the way up until the day before, calculating precisely which day each one hit its lowest point.

Air travelers tend to believe they'll find the lowest of low prices when they book "at the last minute." This, according to all present data, is one hundred percent false.

The researchers found that, on average, a ticket was at its highest price on the day before the flight. The second-highest price was two days before the flight, the third-highest was three days before… and so on, all the way to 13 days before the flight.

This pretty much solidifies the rule that you should NEVER book your ticket within two weeks of a flight... a mistake that 36 percent of CheapAir users made when planning trips.

While the researchers found that 54 days was indeed the magic number for booking on average, they're quick to point out that this isn't a hard-and-fast rule: your flight's "best price" window depends a lot on the specific trip you're taking.

If you're going somewhere incredibly popular at an incredibly popular time - like spring break in Florida, for example - you should book well before the "prime booking window" begins. When there's constant, strong demand for a flight, the researchers explain, airlines have no incentive to lower ticket prices as time goes on. The same principle holds true for flights to hard-to-reach airports in small cities: there's little airline competition here, so ticket prices don't drop nearly as much over their lifespan.

Foreign countries are incredibly popular destinations with hard-to-reach airports, so the researchers suggest booking much earlier than the 54 days recommended for domestic flights. Here are the "magic numbers" for some common international destinations:

Europe: 151 days before your flight
Asia: 129 days before your flight
The Caribbean: 101 days before your flight
Mexico: 89 days before your flight
Latin America: 80 days before your flight

Happy booking, travelers!