It’s not a myth: Timing matters when buying airline tickets! This is true for domestic and international flights. Knowing the best days to buy airline tickets will save you a significant amount of money.

Book your flights on the weekend (not Tuesday)

It used to be true that booking airfare at about 3 p.m. eastern time on Tuesdays was the best way to save money on a flight. This was because airlines often began sales on Mondays, so other airlines would lower their fares by mid-day Tuesday to compete. However, new data shows that nowadays, the best days to buy airline tickets are Saturdays and Sundays, no matter the departing and destination cities. What’s more, the savings by booking on a weekend are pretty substantial. Booking on weekends can save you up to 20%, and booking on a Sunday in particular can save you up to 36%. On the flip side, airline tickets tend to be the most expensive when they are booked on a Thursday or Friday, so avoid those days if at all possible.

Plan to begin your trip on a Thursday or Friday

Aside from booking your airfare on a weekend, the departure date of your trip can also greatly impact the price. While it may be tempting to start a trip the first chance you get, this might not always be the best idea for your wallet. Travelers can expect to see a savings of about 10% for flights leaving on Thursdays and Fridays, which are the cheapest days to takeoff. The money you save can be a pretty big chunk of cash simply by planning for a late-week start for a trip. For whatever reason, if it’s not possible to leave on a Thursday or Friday, the next best piece of advice to save money on airfare is to avoid leaving on a Sunday. Sundays tend to have the highest airline travel prices.

Book your trip at least three weeks before your departure date

Average airline ticket prices get higher as the date of a flight’s departure approaches. This is true no matter the destination in the majority of the world. Make sure to book at least three weeks before you plan to fly to ensure that you’re not overspending on airfare. While last-minute flight deals do exist and can pop up just days before a flight, most of the time this is not going to happen, and it’s an expensive risk to take. That being said, booking too far in advance is not usually going to get you the best deals either. Booking a flight around three weeks in advance of a trip seems to provide the most in terms of savings on a fare.

Stay through the weekend for weekday trips

Mid-week trips should be extended to Sunday to save the most money on airfare. The cost of returning on a Sunday, or even returning on a Saturday late-night red-eye dropped in close to 75% of analyzed flights. The savings came to about 25% in comparison to returning during the week. To put it bluntly, extending your stay through the weekend means fairly hefty savings on the cost of the flight. This is especially true for corporate and business destinations that have a high demand for mid-week travel (like between New York City and London). In these cases, choosing to stay through Saturday night can cut the cost of the airfare almost in half. This is great news, as who doesn’t want to extend their vacation and save money at the same time? That money is better spent on the trip than on the airfare anyway.

Basic economy is not always the best choice

Basic economy seats on a flight — the fares that do not include checked baggage or any other extras — is the lowest fare on any flight. If you know for a fact that you’re not checking a bag, this is a great way to save money. However, if your plans change and you suddenly need to check a bag for even one leg of the flight, you’ll end up paying more. Adding the bag after the initial purchase of the flight pretty much always comes out to cost more than just buying a flight that includes a checked bag in the first place. In short, if you think you’ll need some flexibility on the checked bag issue, the most cost-effective method is to make the decision from the start to go with the fare that includes a checked bag.