The discount travel service recently took a look at more than 917 million — yes, that’s 917,000,000 — transactions in its database with the aim of figuring out the best time to buy inexpensive airline tickets. If you or your employees travel a lot for business, this kind of data could save you some real money this year. So, here are the five biggest takeaways.

1. Prices really change a lot.

According to the study, the lowest fare for any particular trip changed an average of 62 times — or once every five or six days — during the period the trip was available for sale. You should check frequently, sign up for alerts, and then, when you finally buy, don’t look back.

2. The magic number is 70 days…but there’s a caveat.

The best time to book a ticket, on average, is about 70 days before your flight. However, this varies significantly by season. For example, the average best time to buy a ticket for summer travel is 47 days before a flight. The number goes up to 69 days in the fall, 62 in the winter, and 90 days in the spring. Of course, travel on holidays always needs to be booked further in advance, but you’re not asking your employees to travel on a holiday, are you? Tsk tsk.

3. Booking too early is not helpful.

If you like to plan ahead, that’s a good thing. But, unfortunately, it probably won’t save you any money. In fact, it will probably cost you more. The study found that people booking as much as six to 11 months in advance were “almost certainly going to pay a premium for airfare.” How much of a premium? About $50 more on average.

Having said that, those super-early-birds can take advantage of better seating options. Instead of spending too much money by booking known dates too early, schedule a reminder for yourself as you get to about 70 days before the time of travel. Don’t forget to adjust per season.

4. Waiting until the last minute is about the worst thing you can do.

Sometimes it can’t be avoided, but if you or one of your people needs to book a flight within six days of departure, you’re likely going to pay through the nose. The people at CheapAir call this the “Hail Mary” tactic, and it’s about as successful as the football play.

Last-minute fares purchased this way cost an average of $208 more than buying during the “prime booking window” (21 to 121 days in advance). You’ll also likely be sitting in the middle seat between that snoring guy and a woman eating chicken curry. Try to at least give yourself a couple weeks before booking.

5. There is no best day to book, but there is a best day to fly.

After analyzing almost a billion transactions, can definitely tell you that there is no definitive best day to book a flight. The differences day to day were negligible. However, booking a seat to fly on a certain day does make a difference. Your best price will be found if you want to fly on a Tuesday or Wednesday. Ask your salespeople to stick to those days when visiting customers and prospects, and the savings will add up. Sunday is the most expensive — about $76 more on average compared to earlier in the week.

My advice as a frequent traveler?

Being loyal is your best strategy. OK, this is not based on a billion transactions. It’s based on my own personal experiences. I’ve found that picking an airline and sticking with it will pay off in the long run. You may spend a little more and a little less on individual flights, but you’ll rack up points, gain status, save time, and reduce stress when things inevitably go wrong. Play the long game and invest in a relationship. The benefits will outweigh the costs over the long term.