Most "flight deal" alerts have the same problem: they tell you a price _changed_, not whether it's actually _good_. A £520 fare to Bangkok means nothing on its own. Is that cheap? Normal? A rip-off? Without a baseline, "−40%" is just a number someone made up.
Flight Signal exists to fix exactly that. Here's how it works.
We observe prices ourselves, every day
A scheduled job queries licensed fare data for return trips from all five London airports — Heathrow, Gatwick, City, Luton and Stansted — across the destinations we track. Every observation is committed to a version-controlled history: origin, destination, dates, price, and the moment we saw it.
Nothing is scraped. No anti-bot measures are bypassed. It's a first-party dataset — prices we saw, not resold aggregator numbers — which is what makes everything downstream honest.
We build a baseline from that history
For each route we derive a rolling median from the observations themselves, once we hold enough of them. That median _is_ the baseline: the ordinary price for this route right now, computed from real fares rather than a marketing "was" price.
Until a route has enough history, we fall back to a hand-set benchmark — but it's clearly flagged as a cold-start proxy, never presented as observed history. The sample size and window travel with every fare, so you can always see what a claim rests on.
We score — and only the exceptional gets through
A fare's deal score combines how far below its baseline it sits with signals for the number of stops, journey length, trip length, departure airport and departure time. A price is only ever called a deal when the maths says so, and a strict daily cap means you hear about the genuinely great fares, not a dozen mediocre ones.
"Is now a good time?" is a question we can answer
On every destination price-history page we compare the cheapest fare observed in the last ten days against the full distribution of every fare we've recorded on that route. At or below the cheapest quartile, we call it unusually low. At or below the median, fair. Above the median, above typical. The quartiles are on the page, so you can check the call yourself.
What we never do
- No auto-booking, and never any passport or payment-card data.
- No fabricated "was" prices — only distributions of fares we actually observed.
- No misleading structured data on volatile fares.
The full technical write-up lives on the methodology page, and the aggregate numbers are published openly as the London Flight Price Index.
If you'd like the genuinely exceptional London fares pushed to your phone — scored against this exact history, with a booking link — get deal alerts.