Regardless of your travel experience, it can be overwhelming to choose the best site to book flights. The top airfare sites work differently, and they all have dedicated user bases. To find the undisputed best site to book cheap flights, we compared 10 of the most popular travel search engines and flight finders. Here's our 2019 ranking.
1. Skiplagged—Best Flight Search Engine for Cheap Economy Tickets
When searching for the cheapest flights in economy class, Skiplagged returned the lowest price for both the domestic and international itinerary we tested. In fact, the economy class round-trip Skiplagged found between New York and London ($304) was $27 cheaper than the next best alternative (Google Flights, $331). The domestic round-trip Skiplagged found between Denver and New York was also on par with the cheapest options across competitor sites.
Skiplagged's Search Algorithm: Finding Hidden-City Flights
One of the reasons Skiplagged is able to find cheap flights is that exploits a loophole in airline ticketing. Instead of searching only for tickets from City A to City B, it also searches for "hidden-city" tickets—flights from City A to City C that have a layover in City B. For example, if you want to fly from New York to Chicago, Skiplagged may find a cheap flight from New York to Denver that has a layover in Chicago.
No Option to Search by Cabin
One potential drawback to using Skiplagged is that it doesn't have an option to filter by class or to search specifically for premium economy, first or business class tickets. The website will automatically filter your search results by price, which means that cheap economy class tickets will always be at the top of the results page. While this won't be a problem for most people, business travelers will be better served by another option on this list.
2. Google Flights—Best Flight Search Engine for Interface and Search Experience
Google Flights is our runner-up due to its excellent search experience and its consistent retrieval of competitively priced tickets on any itinerary we entered. One of the best features of the service is that it allows you to search for flights across multiple airports with one query. For example, if you're booking a flight to Charlotte, North Carolina, and you're not sure whether you'll be in Boston or New York, Google Flights will let you browse departures from both cities with one search.
Speedy Load Times and Sleek Interface
Of the 10 airfare search sites we evaluated, Google Flights without fail returned results the quickest across dozens of queries. Search results on Google Flights consistently loaded in under a second, while other sites—i.e., Hotwire and Priceline—took upward of 10 to 15 before displaying any flight options. Another draw to using Google Flights is that both the mobile and desktop versions of the service provide an intuitive and familiar interface for people who already use Google products.
Save Money by Booking Each Leg Separately
One of the reasons Google finds inexpensive itineraries is that it allows you to book the departure and return legs of your trip on different airlines. This is helpful in cases where booking two one-way tickets is more affordable than booking a round-trip. While Google Flights didn't invent this concept (sites like Kayak have long offered a mixed-airline itinerary), we found that it was nicely integrated into the service's search capabilities.
3. Momondo—Best Flight Search Engine for International Tickets
Compared to the other airfare sites we evaluated, Momondo performed the strongest when searching for international itineraries, particularly business class tickets. Momondo works by searching for tickets on online ticket agencies—Momondo doesn't sell tickets on its own website—which allows it to find low prices on third-party services.
Book Through Third-Party OTAs
Most of the sites that we evaluated allow users to book tickets directly on their platform or on the airline's website. Momondo only lets you book tickets through online ticket agencies (OTAs), meaning you'll have to complete the sale on a website that may be unfamiliar to you, like Flights Mojo, Globehunters or TravelMint. This shouldn't be an issue in most cases, but it can present a problem if you need to change or cancel your flight (some airlines charge more to change a ticket bought through an OTA).
Mediocre Search Experience, Interface and Site Speed
Compared to our top two picks, Momondo's user experience is a bit lacking. Google Flights loaded its search results significantly faster than Momondo, and Skiplagged's interface had a much cleaner and more modern feel. In general, we recommend using Skiplagged and Google Flights for domestic bookings and Momondo only when searching for international flights.
Honorable Mention: Hipmunk
Hipmunk didn't find the cheapest airfare for any of the itineraries we tested, but in some cases it found cheaper ways to get from point A to point B than flying. When searching for plane tickets between Boston and New York, for example, Hipmunk presented us with an Amtrak train travel option that was more affordable than any of the flights. This is because Hipmunk uses a sort-by-"agony" feature that filters by price, duration and stops to find the easiest way to get to a destination.
Honorable Mention: Kayak
Kayak is a tried-and-true flight search option that has quick load times and solid travel packages for hotels, rental cars and cruises. While it didn't perform as well as Momondo on international flights, it found the same affordable domestic business class itinerary as Google Flights. If you're looking to book a travel package or a domestic flight, Kayak is an excellent option.
Honorable Mention: Southwest.com
For domestic tickets and trips to the Caribbean, the Southwest Airlines website is a must-visit destination. Southwest offers affordable tickets across its route map—and it doesn't allow its tickets to be sold or displayed on third-party websites like Skiplagged, Google Flights and Momondo. As such, you should always check Southwest before booking a domestic economy or Caribbean itinerary on another airline.
How to Get Cheap Tickets, Regardless of Which Search Engine You Use
Even the most-advanced flight search engine can only get you so far. If you want to save money on airfare, your best bet is to plan ahead. Follow the tips and tricks below to maximize your savings:
Fly on a Tuesday or Wednesday
If possible, book the departure and return dates of your trip in the middle of the week, as Tuesdays and Wednesdays are the cheapest days to fly. Flights are more expensive on the weekends and on Mondays and Fridays, because is demand is highest. If you're curious about which days are best to fly for a specific trip, most of the search engines we recommended allow you to see prices for flights on each day of the week.
Book Two Months in Advance
Studies suggest that 54 days ahead of time is the cheapest day to book tickets for an upcoming trip. While you don't have to be this exact, it's advisable to buy tickets at least two months before you plan to fly. Prices start increasing after the two-month mark and skyrocket two to three weeks before the departure date.
Take Your Trip in Off-Peak Season
There are certain times of year when it's much more expensive to fly—think major holidays, long weekends and your state's school vacation week. If you have the flexibility, you can save hundreds by planning your vacation around these busy travel dates and booking your trip off-peak, especially if you're flying to a seasonal destination like Hawaii.