Best sites for cheap flights: Kiwi.com vs Aviasales vs Expedia

Which flight booking site should you use?

The three sites work in different ways, so the cheapest one depends on your trip:

• Aviasales if you want to see as many sellers as possible before you pay. It is a free metasearch engine: it lists fares from airlines and online agencies side by side and sends you to the seller to book. Aviasales says it adds no commission to the prices it shows.
• Kiwi.com if you are flexible and want the lowest possible fare on a route no single airline sells cheaply. It is an online travel agency that searches more than 500 airlines and can stitch together flights of airlines that don't cooperate into one itinerary. You pay a Kiwi.com Service Fee, and on those self-transfer trips the missed-connection risk is yours unless you add its Guarantee.
• Expedia if you are booking a flight together with a hotel, a car or activities. Booking a package can save up to 30% compared with buying the parts separately (savings vary and not every package qualifies), and everything sits in one itinerary with 24/7 support.

If price is all that matters, the practical approach is simple: search your dates on Aviasales to see the market, check whether Kiwi.com finds a cheaper combination, and compare the final checkout totals, not the headline prices.

Metasearch or travel agency: how these sites differ

"Flight booking site" covers two kinds of service, and the difference decides who you deal with if something goes wrong.

A metasearch engine such as Aviasales doesn't sell tickets. It collects fares from airlines and agencies, shows them in one list and passes you to the seller when you press Buy. Payment, the e-ticket, refunds, exchanges and name changes are handled by the airline or agency named on your receipt. Google Flights and Skyscanner work on the same principle.

An online travel agency (OTA) such as Kiwi.com or Expedia sells you the booking itself. You pay the agency, it issues the tickets and you contact it for changes. Kiwi.com books tickets with the airlines on your behalf, and the contract of carriage is between you and each airline.

Neither model is cheaper by default. A metasearch shows more sellers, including agencies that sometimes undercut the airline on the same flight; an agency can offer things a metasearch can't, such as Kiwi.com's self-transfer combinations or Expedia's package discounts.

How to choose: what we compared

For each site we looked at the points that change what you actually pay and what happens after you pay:

• Fees on top of the fare. Does the site add its own charge? Aviasales says it charges no commission; Kiwi.com adds a Service Fee shown in the checkout breakdown; on Expedia, Member Prices and some savings are quoted before taxes and fees.
• How wide the search is. More airlines and sellers mean a better chance of finding the low fare.
• Who handles refunds and changes. The seller you paid, the agency, or a mix.
• Cancellation terms. Cheap fares are often non-refundable whatever site you use; some sites add their own paid options.
• Tools for flexible travellers. Low-price calendars, maps, price-drop alerts and baggage filters help you find a fare you would actually accept.
• Extras. Rewards, bundles with hotels or cars, and disruption protection.

None of the three publishes a fixed price list: every fare is a live quote, so the table's "starting price" describes how you pay.

Aviasales: every seller in one free search

Aviasales has been running since 2007 and describes itself plainly: it doesn't sell tickets, it helps you find the cheapest ones, free of charge. Its help centre says it shows the exact prices quoted by airlines and agencies and does not add a commission. Its Russian site says it covers 2,000+ airlines and flights to 193 countries.

What makes it useful for bargain hunting:

• Baggage shown on every result and a baggage filter, so a cheap fare without the bag you need doesn't mislead you.
• Layover filters and icons for long and overnight connections.
• Low-price calendar and map to find the cheapest days and destinations.
• Price-drop alerts in the iOS and Android apps, which can also follow fares across one or several months.
• Fare rules before you click: opening a ticket shows the seller's exchange and refund conditions.

The downside is the flip side of the model: you buy from a third-party seller, so refunds and changes depend on that airline or agency, and Aviasales' terms say it doesn't guarantee the accuracy of the prices it displays. Always confirm the total on the seller's checkout page, including baggage, seat and payment charges. The Aviasales review covers the filters and the operator in more detail.

Kiwi.com: cheaper routes by combining airlines

Kiwi.com is a flight-focused online travel agency run by Kiwi.com s.r.o. in Prague. It says it covers more than 500 airlines, including low-cost carriers, and processes over 100 million searches a day. Its signature feature is virtual interlining: joining flights of airlines that have no agreement with each other into one itinerary, which can be cheaper than any ticket sold by a single airline.

What you pay and what you get back, per its terms and conditions:

Flight prices can change between your payment and the moment Kiwi.com buys the tickets; it may then ask you to pay the difference, cover it, or cancel and refund you. On some itineraries a paid price lock holds the fare (by default for 72 hours).

The optional Kiwi.com Guarantee adds disruption protection with instant Kiwi.com Credit for a replacement flight if an airline cancels or reschedules, automatic check-in (add passport details at least 24 hours before departure) and support where human agents reply within 3 hours. The Kiwi.com review explains the fare types in full.

The real downside: many refunds and compensations come as Kiwi.com Credit, and on a self-transfer without the Guarantee, a delay that makes you miss the next flight is your problem.

Expedia: flights plus hotel in one booking

Expedia.com launched in 1996 and is part of Expedia Group in Seattle, alongside Hotels.com and Vrbo. It compares flights across hundreds of airlines, but its strength is the rest of the trip: hotels, vacation rentals, rental cars, activities and packages, all in one itinerary you can share.

Ways it can bring the price down:

• Bundle & Save: a package can save up to 30% compared with booking the same parts separately. Savings vary and don't apply to every package, so compare both totals.
• Member Prices: free One Key members get 10% or more off select stays, cars, cruises and activities (before taxes and fees). Note that this covers hotels and cars, not flights.
• Price tracking: alerts when a flight's price drops, plus a Flight Deals map.
• OneKeyCash: earned on eligible bookings, including flights, and spendable on Expedia, Hotels.com and Vrbo. It can't be used on package or Pay Later bookings.

You may still earn your airline's frequent-flyer points on flights booked through Expedia. The downsides: flights, cars and activities follow their suppliers' own cancellation rules, and some savings are quoted before taxes and fees, so the checkout total is the number to compare. More in the Expedia review.

Self-transfer flights: what can go wrong

The cheapest result on a search is often a combination of two unrelated tickets. Kiwi.com labels these self-transfer itineraries, and its terms spell out what that means:

• you collect your checked luggage at the layover and check it in again;
• you will probably pass through customs, so you may need a visa or entry documents for the layover country;
• the second airline is not obliged to rebook you if a delay on the first flight makes you miss it.

That doesn't make self-transfers a bad deal. They work well with hand luggage only, a long layover and a passport that doesn't need a transit visa. Leave several hours between flights, check the visa rules of the layover country before you pay, and decide whether the Guarantee is worth it for that trip.

If an airline does delay or cancel your flight, you may be owed compensation from the airline itself; our guide to flight delay compensation explains how claims work.

How to pay less for the same flight

A few habits matter more than which site you start on:

• Compare the checkout total. Headline prices can leave out baggage, seats, payment charges or service fees. Aviasales shows the baggage allowance on each result; Kiwi.com breaks down carrier price and Service Fee at checkout.
• Set an alert if you're not ready to buy; Aviasales and Expedia both send price-drop notifications.
• Read the fare rules before paying. Most cheap fares are non-refundable on any site; if your plans may change, a flexible fare or Kiwi.com's Flexi can cost less than losing the ticket.
• Bundle when you need a hotel anyway. On Expedia, check the package price against the flight and hotel booked separately.

Once the flight is sorted, see our guides to booking a rental car and choosing a travel eSIM, or browse all travel services.