Flight pricing advice is full of confident folklore, most of it either never true or true a decade ago. Airlines use dynamic pricing models with dozens of inputs, and the ones you can actually influence are few and mostly obvious.
Here is what moves the price, and what does not.
The myths, briefly
Incognito mode does not lower fares. Repeated controlled tests have found no consistent evidence that airlines or search engines raise prices based on your cookies. Prices change because inventory in a fare bucket sells out, which happens whether or not you were looking.
There is no magic day to book. The “book on Tuesday at 3pm” advice comes from an era of weekly fare-filing that no longer operates that way.
There is no universal optimal booking window. The often-quoted figures — 54 days, six weeks — are averages across millions of itineraries and tell you almost nothing about your specific route. Long-haul and peak-season routes want more notice; short-haul off-season routes are frequently cheaper closer in.
The clearing-cache trick does nothing except log you out.
What actually moves the price
Flexibility on dates. By far the largest lever. Mid-week departures are usually cheaper than Friday and Sunday. Shifting by two days routinely changes a long-haul fare by a third.
Flexibility on airport. Secondary airports, and nearby cities. Flying into Milan instead of Venice, or Kraków instead of Prague, plus a train, is frequently far cheaper than the direct route.
Season. The largest single factor and the one people treat as fixed. The difference between a school-holiday departure and one a fortnight either side is enormous.
Route, not just destination. Some city pairs are competitive and some are not. A route with three carriers is priced differently from a monopoly route.
The tools that are worth using
A flexible-date map search — the “everywhere” and month-view searches on the major metasearch engines — is the single most useful tool, because it inverts the question from “how much is this trip” to “where can I go for this money”.
Fare alerts on specific routes, set up months ahead. It costs nothing and it catches sales.
Multi-city search rather than two one-ways, which is sometimes cheaper and sometimes not; check both.
Checking the airline’s own site before booking through an agent. The fare is often the same and the ability to change or resolve a problem is dramatically better.
Error fares and mistake pricing
Genuine, rare, and worth having alerts for. They arise from currency conversion mistakes, missing fuel surcharges or fat-fingered filing, and they can be extraordinary — long-haul business class for the price of an economy ticket.
The practical rules: book immediately and separately, do not book connecting flights on the same itinerary until the ticket is confirmed, do not call the airline to ask if it is real, and wait 24 to 48 hours before booking anything non-refundable around it. Airlines sometimes honour these and sometimes cancel them, and the legal position varies by jurisdiction.
Positioning and hidden-city
Positioning flights — taking a cheap short flight to a city with a much cheaper long-haul fare — is legitimate and often saves a great deal. Leave a long buffer, and book the two legs separately with the understanding that a delay on the first is your problem alone.
Hidden-city ticketing — booking A–B–C and getting off at B because it is cheaper than A–B — works, and it breaches the airline’s conditions of carriage. Consequences range from nothing to a closed frequent flyer account. It also cannot be done with checked luggage and cannot be done on a return, because missing a segment cancels the rest of the itinerary.
Budget airlines, honestly
The headline fare is not the price. Add cabin bag beyond a small personal item, checked bags, seat selection, and card fees, and a €19 fare is frequently €90.
They are still often the cheapest option, and the way to keep them so is to travel with one bag that genuinely fits the stated dimensions — which are enforced at the gate with a metal cage and a charge that costs more than the flight.
Also check which airport the fare uses. Several “London”, “Paris” and “Milan” airports are an hour and a bus fare from the city.
The things worth paying for
A direct flight on a long journey, because a missed connection costs you a day and possibly a night.
A proper connection buffer — at least two hours internationally, more at a large hub or where you must clear immigration and re-check bags.
A single ticket rather than two separate ones for a connection. On one ticket, a missed connection is the airline’s problem. On two, it is yours entirely, and this is the most expensive mistake in this article.
Refundable or changeable fares when the plan is genuinely uncertain, which is more often than people admit.
Onward ticket requirements
Many countries require proof of onward travel, and airlines enforce it at check-in even where immigration would not have asked. Options: a cheap refundable regional flight cancelled after arrival, a bus or train ticket, or one of the services that rent a genuine ticket for 48 hours.
This catches out one-way travellers constantly, and being refused boarding for it is a bad way to start a trip.