Under the Hood: Improving Flight Search at Expedia

By John Kim & Aman Bhutani

In this blog, we’re taking a look under the hood at Expedia. A closer inspection of our travel engines will reveal the millions of calculations and computations being made every millisecond so travelers everywhere can quickly and easily book a great vacation. It is here that we’ll share more about how we are developing smarter solutions and recommendations to guide our customers to the trip they want to book. Welcome.

Most people begin planning their trips with flights. We’ll start there too.

A typical customer searches for a flight up to an average of 48 times before booking. Here at Expedia, we strive to bring that number down by surfacing the most relevant results that can include alternative surrounding airports, day, or time of travel.

For a given round trip flight search between two destinations, there can be billions of flight combinations, even when only looking at a single departure and return date. Expedia whittles that down, returning the best sixteen hundred results in the form of 40 departing and 40 returning flights.

Yet as every traveler knows, each search begs more questions than it answers. Is the best flight for you flying out of different airports? Would adjusting the length of your stay or departure day save you any money?

Take a basic flight search: Seattle to Miami for a five to seven day trip. To find the cheapest round trip fare in a 30-day period, you could conduct 3 searches (a search for a 5-, 6- or 7-day trip) for each day in that period, which would quickly get you to 90 searches.

Now, imagine you had the inside knowledge that traveling to Fort Lauderdale is a great alternative to Miami, suddenly you find yourself having to do another 90 searches to find the best prices. Now combine those airports and you have 180 combinations. Adding other departure or arrival airports such as Portland or Palm Beach pushes the number over 500.

With an average search taking at least a minute, doing all this research would take you hours. With thousands of price updates taking place every hour, you’ll have to start again by the time you finish since the prices and availability will have changed. It’s no wonder why people end up searching 48 times!

Meet Expedia’s New Flight Recommendations

By leveraging the over three billion flight searches performed worldwide on Expedia, Flight Recommendations looks for patterns to help travelers with their next search.

In fact, we see our users follow very distinct habits. To start, travelers look to depart and return on specific days, such as leaving on Sunday and returning on Friday. They will then search leaving Saturday or returning on Thursday, all in hopes of finding a more convenient or cheaper fare. Combine this with searches for alternate airports and suddenly travelers find themselves overwhelmed with all the possibilities.

By following the patterns of how our travelers search, then book, and finding alternative airports/dates in those searches, Flight Recommendations surfaces the best options. We look for similar deltas for departure and arrival days and surface them as search recommendations. Our goal is to make it easy to see all the best options at a glance so travelers can choose what’s right for them whether it’s price or convenience.

Recommending alternate flights to travelers isn’t new. You’ve probably seen this in the form of fare calendars. However, this system doesn’t help travelers with anything beyond a snapshot of a saved price. Our team is looking at real purchasing patterns, of real travelers at scale so we can help you find desirable, bookable flights for less.

With each recommendation, we track the effectiveness, value, and accuracy of the prediction against real booking information and adjust them to best benefit our customers. These adjustments could take the form of different data, adjusted thresholds, or additional factors. The algorithm is always evolving and is the backbone of the recommendations feature.

Going on vacation is fun. Planning a vacation, however, is a multivariate optimization problem that some of the smartest engineering minds are working on. Together, we can advance the science of travel to help consumers save time and money. The opportunities we have to identify patterns with our data are endless and we are just barely scratching the surface. Stay tuned!

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About John Kim

John Kim is the Chief Product Officer at Expedia. He is a seasoned and accomplished product and marketing executive with over 17 years experience as a digital media executive. John has a deep domain expertise in online and mobile search, local, advertising, analytics, gaming, and social media.

18 thoughts on “Under the Hood: Improving Flight Search at Expedia

  1. So far, every recommendation that I have looked at are all at least 150 – 200 more than what you recommend. If you are going to make recommendations, please be accurate!

  2. Okay,

    I have hit you recommendations at least ten times now while searching for a flight to Hawaii. So far, the results have been AT LEAST $100 more than you say in your window. Am I missing something? It even says average, and, I am not coming close.


  4. None of the recommendations works out. Though they say I can go from Atlanta to Houston for $236 avg., there are no actual flights under $302.00.

  5. When I click on the alternative flights (leave 2 days early, return 1 day earlier) that shows a lower price that price never comes up. How do I book at the lower price?

  6. Hi everyone – We appreciate your feedback and looking forward to continuing to improve this feature so you have a great shopping experience.

    Flight recommendations are based in part on the average prices that our customers have paid for flights. At times, the recommendation price may be different than live pricing due to the large number of pricing changes that occur in the flight shopping marketplace on a daily basis. However, each recommendation represents a pointer to a search where the best values have historically been. As the recommendations product is used and tuned over time the alternatives returned will get more accurate and effective.

    Brian Keffeler
    Senior Product Manager – Mobile, Expedia

  7. I understand the explanation given, but it is still very frustrating to be constantly getting recommended rates that have no current basis in reality. It ends up wasting much time for me to click on these recommendations only to find that the actual fare is hundreds more. Please work on improving this product.

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