Scott Keyes from "Scott's Cheap Flights" joined ABC 7 Chicago Friday to talk more about it.
You find the best deals if you book two seasons in advance, similarly to how off-season clothes are on sale, he said.
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Despite the ongoing COVID pandemic, Keyes said it's still a good idea to book in advance because airlines have eliminated most change fees.
Keyes published a book earlier this year, titled "Take More Vacations," which can be found on various sites online.