While it’s relatively easy to find all categories of hotel at discounted prices the day of or a couple of days be your trip, airlines play a very different game.
At least U.S. airlines prefer to fly an empty plane anywhere in the world before letting you book such route at a substantial discount. It would be nice to see mark downs on any class dear the departure day. If we had real competition, we would see “clearance sales” for all kinds of flights.
Using Google Flights you will quickly see how expensive traveling during the holidays or close to them can be.
If you keep looking, you will find that good to great deals can still be found.
In this case, Mexico City and San José, Costa Rica appear in green meaning the prices are good to great.
Other things to keep in mind, my search excludes flights with stops, and basic economy flights. If those 2 things don’t bother you, you would be able to find even cheaper deals.
Another option would be to use miles to pay for your flight. I was able to find great availability and pricing for my preferred destinations using United miles, but I gave up trying to use a companion pass or SkyMiles on Delta for the same dates.
As you can see, if you wanted to get away tomorrow you still can!