For most airlines, the earliest you can book a flight is about 11 months before your departure date. Unfortunately, domestic fares tend to remain high and steady for about 7 months prior to departure. Airlines just aren't pressured to fill seats, which is why they don't offer fare sales that far in advance.
So when is the best time to book your travel? The prime ticket-purchasing window starts 104 days before a flight. After that, fares fall slowly and steadily until they reach their lowest point, which is 54 days before departure. Prices then begin to climb again, but stay within $10 of that low number until 29 days before the flight.
For those of you who missed the prime-booking window, your best chance of finding a last-minute deal on a Fourth of July flight is about 21 days in advance. Booking this week could potentially net you a 17% savings.
So, if you want to get away on Independence Day, make sure to purchase your Fourth of July airline tickets at the right time to get the right price.