Route anomalies, and why they matter

Comparison sites are optimised for the question they expect you to ask: cheapest itinerary from A to B on date X. They are not optimised to surface why one option is dramatically cheaper than the others — which is exactly the information you need to decide whether to take it.

Fifth-freedom segments

A fifth-freedom flight is a route flown by a carrier whose home country is neither origin nor destination — Ethiopian Airlines selling between Dublin and Washington, Emirates between Newark and Athens. These segments price aggressively because they exist to feed traffic into the carrier's hub network. The seat is often a step up from the alliance equivalent, sold at a step down.

Mismatched fare buckets

Sometimes a long-haul economy seat is sold in a fare bucket whose rules belong to a different cabin. The bucket allows free changes; the cabin doesn't include checked baggage. The interaction is flexibility for free at the price of comfort — useful for short trips, painful for long ones. Read the fare basis, not the marketing label.

Open-jaw arbitrage

Booking a one-way from a "cheap" country (often a cabotage exception, or a market the airline is fighting for) plus the return from your actual departure point. Pair this with positioning flights at your own risk — but the math is sometimes irresistible.

The point

None of this is news to a frequent traveller. What changes when you have continuous market surveillance is that you stop having to look for these anomalies. They surface on their own, at the price point you cared about, on the route you actually fly.