Useful info...

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 of the lowest price they’ll ever reach. [...]

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