The best sites for cheap flights mostly aren't selling you anything. Google Flights, KAYAK and Momondo are search layers that hand you to an airline or an agency to pay. Going doesn't sell tickets either. It sells you the alert.

That difference decides what each one is good at, and it's published in their own words. We read those pages on September 12, 2026. Four of the five explain themselves in detail. The fifth, Skyscanner, blocked us at every door that mattered.

What Each One Actually Is

Google Flights is a hand-off. It says it "allows you to book flights from more than 300 airline and online travel agency partners," and that when you pick a fare, "you'll usually be taken to the airline's website or online travel agency to complete the transaction."

KAYAK is blunt about it. Asked whether it's a travel agency, its help page answers: "No, KAYAK is not a travel agency. We're a travel search engine (also called a metasearch engine) that helps you find and compare options from hundreds of travel sites, then book directly with the provider you choose."

There's one exception it names: "In some cases, you can complete a booking with a third-party travel provider without leaving KAYAK's website. This is listed as the 'Book on KAYAK' option in the search results."

Momondo describes itself as "a travel metasearch site that finds and compares the best offers on flights, hotels, car rentals and package holidays," and adds "We are not a travel agency, and we don't sell tickets." It's managed by KAYAK, and both sit inside Booking Holdings.

Going is a different product entirely. Its own page says: "No, Going is not a travel agency, flight search engine, or travel booking site. Instead, we find deals departing from your chosen US airports and send you an alert when we find a deal that passes our Bestie Test."

Skyscanner we can't tell you about with confidence, and that's covered at the end.

How Each One Finds a Cheap Fare

Google sorts twice. It shows results in two tabs, "Best" and "Cheapest." The Best tab picks "the best trade-offs between price, convenience, and ease of booking." The Cheapest tab "prioritizes low prices, and includes additional itineraries and prices from online travel agents," with trade-offs Google names: self-transfer of luggage between connections, or flying out of one airport and back into another.

It also predicts. Google's tips include "Prices are unlikely to drop before you book," "Prices are less than usual" and "Prices are likely to increase," each based on past price trends rather than certainty.

KAYAK forecasts a week ahead. Its Price Forecast "predicts whether flight prices for your specific route are likely to go up or down within the next 7 days, based on historical data from over a billion travel searches we analyze each year."

Worth knowing: KAYAK's own pages disagree on the horizon. The help pages say seven days, while its About page says "within 30 days." We're quoting the seven-day figure because it appears on the pages that explain the feature.

KAYAK's other tools are more concrete. Hacker Fares combine "two separate one-way tickets (often from different airlines) instead of a traditional round-trip booking." Price Alerts trigger on "a significant price change, typically a 10% increase or drop." Explore shows "prices that other users found in the last 48 hours," which KAYAK calls "snapshots of recent deals rather than guaranteed fares."

Momondo estimates, then makes you search again. Its Price Calendar "shows you approximate prices for your flights based on previous searches made on momondo," and Momondo warns that "in order to see the most up-to-date and accurate prices, you need to click on 'Search these days' once you've selected new dates."

Its Flight Insights tool breaks prices down by "days to departure, time of day, day of the week, seasonality, airport and airline company."

Going waits for the deal to come to you. It watches "airfare to over 900 destinations," searches only US departures including Puerto Rico, Guam and St Thomas, and says "none of the deals we send are only available at the last minute; most deals are for travel 2-9 months in the future."

Going's plans are published: a free Limited tier, Premium at "$4.08" a month "Billed annually at $49," and Elite at "$16.58" a month "Billed annually at $199." Mistake fares and points deals sit in the paid tiers, and there's a 14-day trial.

One caution on Going's savings claims. Its how-it-works page says Premium members "save an average of $550 on each international flight," while its Premium page says $500 for the same claim. Treat either as marketing, not a forecast.

Who Pays, and Why That Matters

Free products have a funder. Two of these sites say exactly who.

KAYAK answers it directly: "KAYAK earns revenue from our travel partners and advertisers, not from you," through "Commissions from partners" when you click through and book, plus advertising. It adds: "You never pay KAYAK directly for flights or hotels."

Momondo is equally clear: "momondo only makes money when a successful completed booking is carried out on the site you are redirected to, or on a click-through basis, as we receive a referral fee. These referral fees are paid by our partners, we never charge you any fees or commission."

Momondo also promises something worth having in writing: "The prices you see are never affected by your searches, no matter how many you make. We do not use cookies to adjust or increase prices."

Google tells you what doesn't happen: "Travel partners don't pay Google to appear in the list of flights, and the list order isn't influenced by Google's relationships with these partners." What it doesn't publish on those help pages is how Google itself earns from Flights.

Going earns from the membership. It doesn't publish whether it also earns from the booking links in its emails.

Ranking Isn't Neutral Everywhere

This is the part most roundups skip, and it comes from the sites themselves.

Momondo says its flight results use "an algorithm to determine which one will be displayed first," and that the algorithm "takes into account user experience, customer satisfaction, compensation we receive and user rating."

On hotels it goes further: "We also factor the average revenue potential of each hotel into our recommendations. Within a hotel listing, we order our results based on an internal algorithm that balances the prices and our revenue for the results shown."

Google's booking-link order has its own logic, weighing "Whether the link has a price," the price offered, and "Whether the link is an airline or an OTA link," because "Google's data shows that users prefer airline links."

None of that makes these tools untrustworthy. It means the first result is a recommendation, not a verdict, and the cheapest option is often a line or two below it.

The Google Price Guarantee, in Its Actual Terms

Google runs a price guarantee on some itineraries, and the figures live in its Additional Terms, not in a help article.

What it covers: itineraries "marked in Google Flight Search with the 'Google Price Guarantee' badge," bought from participating airline partners, "only available for one-way and round-trip itineraries departing from the U.S." Multi-city trips are excluded.

What you get: "a payout equal to the difference between the Price Guarantee price and the lowest price available for the same itinerary." The price difference "must be $5 or more," payouts run through Google Pay, and you're capped at "a maximum Payout amount of $500 in the aggregate across all eligible itineraries in a given calendar year."

The conditions that catch people: you may hold only "three confirmed Price Guarantee bookings at a time," you must complete the travel, and "If an eligible itinerary is changed or canceled by you or the airline after the initial booking, then the itinerary is no longer eligible."

One warning. Google has two versions of these terms live, and the older 2023 copy is built around the retired "Book on Google" checkout. The dollar figures match, but the booking rules don't. Read the 2024 version.

The One We Could Not Read

Skyscanner's corporate pages load. Everything that would answer a real question does not.

Its help centre returned HTTP 403 to us on every attempt. Its homepage, its Everywhere page, its business-model page and its Whole Month explainer all returned HTTP 200 with an empty JavaScript shell and no readable text.

So we can quote its marketing promise, "no hidden fees, no secret charges, no added cost to you," and its claim to search "billions of prices." We can't tell you how Whole Month picks its numbers, how Skyscanner earns, or whether it sells the ticket or hands you off.

Those answers exist on Skyscanner's site. They just wouldn't load for us, so they're not in this guide. Our older Priceline versus Skyscanner comparison covers what we documented before.

Small Print Worth Knowing

A few lines from these sites change how you read a result.

Google's prices aren't live. It says flight prices "are updated approximately once every 24 hours." The fare you click may have moved.

Google flags split tickets. When two carriers have no agreement between them, it labels the pairing "Separate tickets booked together." Treat that like a Hacker Fare. You own the risk if leg one is late.

KAYAK's Fee Assistant only estimates. It "estimates baggage and payment fees based on what you'd pay on the provider's site." KAYAK says plainly that it "does not add baggage to your reservation. It's a planning tool only."

KAYAK's flexible dates are narrow. Its flexible search "show flight deals up to 3 days before and after your selected departure and return dates." For a wider window, use the price calendar.

Momondo filters some results out. It says it aims for an exhaustive list, then adds: "sometimes we decide to filter out poor quality results." So a missing fare isn't always a missing flight.

Going screens the airlines. It says: "We don't send out deals on budget airlines with poor customer ratings." That's a quality filter, and it's also why some cheap fares never reach your inbox.

None of this makes the tools worse. It makes them tools. Read the label, then book.

How to Actually Use Them

Search two, book one. Run the route through Google Flights and one of KAYAK or Momondo. They surface different OTA inventory, and the gap is often real money.

Then book direct where you can. Every one of these sites tells you the booking lives with the airline or agency, not with them. Momondo says it plainly: "momondo cannot be held responsible for the customer service levels of our suppliers."

Treat Hacker Fares as two trips. KAYAK says the tickets are independent, and "If one flight is canceled or changed, the other airline isn't obligated to accommodate you on the other ticket."

Use price tracking instead of refreshing. Google emails you when a tracked route moves. KAYAK alerts on roughly a 10% swing.

Pay with a card that earns on airfare. The search tool doesn't change what you earn. The card does.

Sign in before you compare. KAYAK keeps a set of rates it calls Private Deals, described as a way to "View exclusive prices that travel providers previously kept private." Signing in is free.

Don't read a blank price as no seat. Google says itineraries "without prices appear below all priced results." Sometimes the flight exists and no partner will sell it to you through that surface. Check the airline directly before you rule the routing out.

For the Google side specifically, our Google Flights guide and our power-user walkthrough go deeper, and our piece on Google's AI flight deals covers the newer tooling. If the goal is a long-haul bargain rather than a specific route, our guide to unlocking cheap international flights is the better starting point.

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Sources

  1. Google, Travel Help articles on finding flights, best fares, booking options and price tracking (read 2026-09-12): 300 plus partners, the hand-off to airline or agency to complete the transaction, the Best and Cheapest tabs, the price insight tips, link ranking factors, and the statement that travel partners do not pay for placement
  2. Google, Price Guarantee Additional Terms of Service, last modified 10/01/2024 (read 2026-09-12): badge requirement, US departures only, no multi-city, payout equal to the price difference, $5 minimum difference, $500 aggregate annual cap, three confirmed bookings at a time, Google Pay payout and the completion of travel requirement. An older 2023 copy of these terms is also live and is built around the retired Book on Google checkout
  3. KAYAK, help pages on about, pricing, search and bookings (read 2026-09-12): not a travel agency but a metasearch engine, the Book on KAYAK exception, Price Forecast over the next 7 days with a conflicting 30 day figure on its about page, Hacker Fares as two separate tickets, Price Alerts triggering on roughly a 10% change, Explore showing prices found in the last 48 hours, and the revenue answer covering partner commissions and advertising
  4. Momondo, help and about pages (read 2026-09-12): metasearch that does not sell tickets, Price Calendar and Flight Insights as estimates from previous searches, Price Forecast over seven days, the referral fee and advertising revenue model, no cookie-based price inflation, and the ranking statement that the algorithm accounts for compensation received and hotel revenue potential
  5. Going, how it works, premium and elite pages (read 2026-09-12): not a travel agency or booking site, US departure airports only, deals typically for travel 2 to 9 months out, no budget airlines with poor ratings, plan tiers at $0, $49 billed annually and $199 billed annually, the 14 day trial, mistake fares in paid tiers, and the differing $550 and $500 average international savings claims
  6. Skyscanner, about us page readable while the help centre and feature pages were not (attempted 2026-09-12): help.skyscanner.net returned HTTP 403 to every request, and the homepage, Everywhere page, business model page and Whole Month explainer all returned HTTP 200 with an empty JavaScript shell, so its Whole Month wording, revenue model and whether it sells or hands off remain unsourced

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