When planning your next vacation, keep in mind the intriguing new online booking platform called GetGoing.

Built for leisure travelers with some flexibility in terms of destination, GetGoing offers a “Pick Two, Get One” system, which results in air fares 20-40 percent below those found elsewhere online.

So, if you are planning a trip to Europe, you might pick Paris and Rome, especially if you are planning to visit both anyway.

That’s the only uncertainty built into the process. Unlike Priceline or Hotwire, you can specify the date, time of day, and number of stops for your flights. You just have to be willing to accept either of two possible destinations.

“Then we show your two options, based on your specifications,” explains CEO Alek Vernitsky. “We flip a digital coin, it’s completely random, and you get an instant itinerary.”

This system works for GetGoing’s ten airline partners, because roughly 20 percent of seats on their flights currently are empty. They’re willing to fill up those empty seats with leisure travelers as opposed to offering more incentives to business travelers, who, it is assumed, will pay full freight.

“Having options–being flexible about where you go–is one of the few ways that proves to airlines you are not a business customer,” explains Vernitsky.

“This is a segmentation tool for the airlines to fill those 20 percent of seats that are empty,” adds VP, Communications Robb Henshaw. “It’s a big business–160 million seats worth $25 billion annually in the US alone. For the airlines this incremental revenue changes the game.”

GetGoing, a Y Combinator startup which just launched last month, already offers flights to 2,000 destinations in more than 50 countries. In order to prove to consumers that its deals are the best available, the site displays the comparable fares from all the competitive sites in a pop-up with a link back to the competitor sites, so you can verify the fare differential.

“I didn’t want to play a game by showing deals that sound good but aren’t real,” says Vernitsky. He’s betting this type of transparency will build loyalty to the site over time.

You can sign into the service either with your email address or with Facebook. The advantage with the latter option is finding out how many of your friends have visited the places you are considering as your two options.

Early adopters have revealed at least one surprise. The team expected 25-35-year-olds to be the largest group, and they are, with 32 percent of bookings to date. But right behind them are retirees, with 25 percent of the bookings.

The top destinations so far are beaches (let’s roll the dice–Mexico or Hawaii?)

SoMA-based GetGoing has about 30 employees, who are working on native smartphone apps and personalization, among other initiatives, as well as plans for adding in hotels to the service this summer.