We get this question all the time: "I saw a flight to Lisbon for $239. Should I book it?"
The honest answer is usually no — but not because the price is wrong. Because the fare and the trip are different things, and the cheap fare is often the cheap fare for reasons you'll notice the second you actually try to take it.
Here are five tests we run on every flight before calling it a Fareduck deal. The first three are arithmetic. The last two require judgment.
1. Is the price actually below typical for the route?
A $400 round trip JFK → Lisbon in May is unremarkable. A $400 round trip JFK → Lisbon in August is excellent. Same dollar amount, vastly different deal.
Every route has a typical price band that shifts by season, day of week, and how far in advance you book. We track the band per route and flag anything below the 25th percentile as worth surfacing — adjusted for season.
Rule of thumb for users without our data: check Google Flights' price-history chart for the route + month. If the fare is below the historical low, it's probably real. If it matches the typical, it's a quote you can probably find any day.
2. Are the dates plausible?
A deal you can't take isn't a deal. We look for fares that:
- Depart on weekdays your preferences allow (Fri/Sat/Sun by default — most people travel weekends)
- Return within your stated trip-length window (4–10 days for most people)
- Aren't peak-conflict dates (Thanksgiving week, Christmas, New Year's Eve — these have their own pricing dynamics)
- Aren't shoulder-season "looks like a deal but the destination is unbearable" picks (Phuket in monsoon season, Madrid in August)
If you've ever seen an absurdly cheap fare and realized it's a Tuesday-to-Tuesday trip in November to a place that closes for the off-season, you know what I mean.
3. Is the routing tolerable?
A $300 round trip from Denver to Tokyo with a 19-hour layover in Houston is not a deal. It's two days of your life you can never get back.
Our score model heavily penalises:
- Total journey time over 24 hours for international
- Layovers over 5 hours (with carve-outs for "stopover programs" like Iceland or Reykjavík, which are actually features)
- More than one stop on routes where direct or 1-stop exists
- Self-transfer layovers across airlines that don't interline (you carry your bag and lose it if delayed)
If the deal saves you $200 but costs you a day, it's not a deal.
4. Will you actually enjoy the destination this time of year?
This is where most generic "cheap flight" newsletters fall down. They send everyone to Lisbon, Bangkok, and Tokyo regardless of who's reading.
A great deal to Bangkok in August (rainy season, every street vendor closed) is worse than a fair deal to Lisbon in May. The destination quality at the dates is part of the deal.
We use your travel persona to weight this. If you said "I like quiet walking trips in food cities," we'll favour Lisbon over Bangkok on equal price. If you said "I want hot beach weather and parties," it inverts.
This is why the Fareduck digest isn't just "cheapest fares this week." It's "cheap fares that match your shape."
5. Is the carrier going to actually fly you?
Some of the cheap fares you see on the big aggregators are operated by ultra-low-cost carriers (ULCCs) or small charter operations with limited frequency. The fares are real, but:
- Cancellation rates are 2-4x higher than legacy carriers
- Re-accommodation when something goes wrong is often nonexistent
- Schedule changes happen routinely up to the week of departure
- Bag fees, seat fees, change fees can double the effective price
We don't blanket-exclude ULCCs (some people are fine with them), but we flag them clearly and the heuristic ranker drops their score. Loyalty status with a legacy carrier outweighs a small price advantage with a ULCC every time.
How to apply this yourself
Even if you don't sign up for Fareduck, here's the manual test:
- Check price history on Google Flights for the route + month. Below historical low? Good.
- Mentally book the trip before checking out. Can you actually get to the airport, take time off, and enjoy the destination on those dates? If you're hesitating, it's not your deal.
- Add up the total journey time door-to-door. If it's > 24 hours one-way and you're not flying internationally, something is wrong.
- Look up the destination's weather for the months in the fare. Off-season cheap is often off-season for a reason.
- Check the operating carrier, not just the marketing one. A "United" code-share operated by a small regional you've never heard of behaves like the small regional, not like United.
If a fare passes all five, book it. If it only passes #1, it's a low price, not a deal.
If this kind of thinking matches yours, Fareduck does exactly this for you — automatically, weekly, free. Sign up; your first digest lands within a week.
— The Fareduck team