Looking to take a trip this summer with your family but worried about the cost? A new survey by FareCompare.com offers several tips to help travelers save money when planning a vacation.

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When booking a trip, airfare prices are often subject to change without warning. Rick Seaney, cofounder and CEO of FareCompare.com, says “every second you make a new search it can be a different price.”

“There’re four airlines in the US that control about 80 percent of traffic in the US that’s the new American with US Airways, United, Continental, and Southwest- those airlines file airfares all throughout the day.” Seaney said.

Although airfare constantly changes, there are specific times throughout the week when airfare prices are always the cheapest.

“The most ideal time to shop is Tuesday at 3 p.m. eastern time,” Seaney said. “The reason for that is two-thirds of all sales for the airlines are filed late Monday night. All the other airlines scrambled to match those sales and it takes them all morning to match.”

The shopping window stays open until Thursday afternoon.

Even on Tuesdays, prices are highest six to eight months in advance. Seaney said three months before a flight is the best time to purchase a ticket. There are even more strategies in place when shopping for a family vacation.

“If you’re shopping for a family of four, there is a quirk in the reservation system that says everybody has to be at the same price so if there are tow cheaper seats at the price the reservation system automatically bumps everyone to the higher price point. So the first thing you should do it check the price of one ticket and see what the price is, then check for four people and see if there is a difference,” Seaney said.

If you split your purchasing, you can save money.

So where’s the best place to take your family this summer?

“This is probably the best time to ever fly to Europe in the last ten years," Seaney said. "Just pack light and have a great European trip.”