There’s no shortage of sites promising to find you cheap flights. The problem is that most of them are just reskinned versions of the same search engine, and few actually surface the deals that save real money.
We spent three months testing 15 different flight deal tools — running identical searches, tracking price accuracy, and measuring how often each tool found fares that others missed. Here’s what actually worked.
What Makes a Flight Deal Tool “Good”
Before diving into specific tools, it helps to understand what separates a useful flight search engine from a glorified ad platform.
The best tools do three things well:
- Search across multiple airlines simultaneously — including budget carriers that don’t appear on every platform
- Track prices over time — so you can set alerts and book when fares drop
- Surface “mistake fares” and sales — the rare pricing errors and flash sales where you save 40-70%
Most tools only do one of these. The ones on this list do at least two.
1. Going (formerly Scott’s Cheap Flights)
Going remains the gold standard for flight deal alerts. Their free tier sends 3-5 deals per week to your inbox based on your departure airports, while the premium tier ($49/year) unlocks mistake fares and peak-season deals.
What stood out in testing: Going found 4 deals under $300 round-trip to Europe in a single month from a mid-sized US airport. No other alert service matched this volume.
Best for: Flexible travelers who can book within 24-48 hours of a deal dropping.
Limitations: You’re reacting to deals, not searching for specific routes. If you need to fly to Paris on specific dates, this isn’t the tool.
2. Skyscanner
Skyscanner’s “Everywhere” search is criminally underused. Enter your departure city, select “Everywhere” as the destination, and choose “Cheapest Month” — it scans every route and shows the cheapest options globally.
What stood out in testing: Consistently found fares $20-80 cheaper than Google Flights for the same routes, particularly on budget carriers and mixed-airline itineraries.
Best for: Planning trips around price rather than destination.
Pro tip: Use the “Direct flights only” toggle strategically. Sometimes a 1-stop flight on Skyscanner is cheaper than a direct flight anywhere else — and the layover adds a free mini-destination.
3. Google Flights
Despite being the most popular flight search engine, most people use only 10% of Google Flights’ features. The price tracking, date flexibility grid, and “Explore” map are powerful tools hiding in plain sight.
What stood out in testing: The price graph feature predicted fare drops with surprising accuracy. When it showed a green “Prices are low” indicator, fares increased within 48 hours about 70% of the time.
Best for: Searching specific routes with date flexibility. The calendar view showing prices across an entire month is unmatched.
Pro tip: Always use the “Track prices” toggle. Google’s fare predictions are right more often than they’re wrong, and the email alerts are genuinely useful — not just marketing.
4. Momondo
Momondo is owned by the same company as Kayak but consistently surfaces different results. In our testing, it was particularly strong for international flights involving budget carriers or codeshare routes.
What stood out in testing: Found the cheapest option for 6 out of 10 international route searches. Particularly good for flights involving connections in smaller European hubs.
Best for: Complex international itineraries where you’re connecting through non-obvious cities.
5. Kiwi.com
Kiwi’s “Nomad” feature lets you enter multiple cities and it builds the cheapest route connecting them all. This is the only tool we found that handles multi-city trips without charging a premium.
What stood out in testing: Built a 4-city European itinerary (London → Barcelona → Rome → Amsterdam) for $340 less than booking each leg individually on Google Flights.
Best for: Multi-city trips and round-the-world routes.
Caution: Kiwi books some connections as “self-transfer,” meaning you’re responsible if a delay causes you to miss the next flight. Always check this before booking.
6. Hopper
Hopper’s mobile app uses historical data to predict whether fares will go up or down. Its “Watch” feature monitors prices and sends push notifications when it’s time to buy.
What stood out in testing: Price predictions were accurate about 65% of the time for domestic US flights. Less reliable for international routes.
Best for: Domestic flights when you have flexible dates and can wait for the right moment.
7. Secret Flying
Secret Flying specializes in mistake fares and error pricing — those rare moments when an airline accidentally lists a $2,000 flight for $200. These deals are time-sensitive and disappear fast.
What stood out in testing: Posted 3 genuine mistake fares during our testing period, with savings of $500-1,500 per ticket. However, only about 40% of posted deals were still available when we checked them.
Best for: Extremely flexible travelers who can book immediately when a deal appears.
The Bottom Line
No single tool finds the cheapest flight every time. The strategy that saved us the most money was combining Going for passive deal alerts with Skyscanner or Google Flights for active searching on specific routes.
If you’re booking one or two trips a year, start with Google Flights and Skyscanner — they’re free and cover 80% of use cases. If you travel frequently or want to catch those rare 50-70% off deals, add Going’s premium tier. The $49/year pays for itself with a single deal.
The worst thing you can do is book the first price you see. Every search should check at least two of these tools. The 5 minutes of comparison shopping regularly saves $50-200 per flight.