When to book cheap flights online

When to book cheap flights online: start with a better question

Many people searching for when to book cheap flights online hope for one rule: a weekday, a number of weeks before departure, or a time of night. In general, such rules are hard to rely on, and the sources this article draws on do not offer one. Fares tend to shift for reasons travellers cannot see, so any calendar shortcut is at best a rough habit rather than a guarantee.

A more useful question is this: how do I recognise a good fare when it appears, and what must I check before I act on it? That turns the decision from guessing where the market is heading into judging one specific offer. A fare is only cheap compared with something else: what the route usually costs, what the whole trip will cost, and whether the dates actually suit you. The sections below work through those comparisons and the limits on any price you find online.

Judge a fare against a reference, not a feeling

The clearest signal that it is a good moment to book is a fare well below what the route normally costs. Flare, which surfaces flight deals from a traveller's departure city, builds this principle into its product. Its methodology page explains that its automated deal pages only include a fare once it sits at least 30% under the reference price its monitoring uses for that route. That is an automated product qualification threshold, applied by the page generator, not an editorial judgement. It does not predict where prices will go next, but it shows the right habit: define what normal looks like first, then measure an offer against it.

That reference has limits worth understanding. According to the methodology, it is an internal measurement: usually a trimmed median of the route's observed history, and on some long-haul routes a lower-confidence fallback calibrated on distance. It is not a universal market average. A fare flagged as below Flare's reference is therefore not automatically below your own baseline or below what the wider market charges, so treat the signal as a prompt to check, not a verdict.

Your own baseline matters too. Without one, a price can feel low simply because it is lower than the last one you saw. Searching a few date combinations, nearby airports and alternative destinations gives you a rough picture, and the more options you are willing to compare, the more likely you are to find a fare that is genuinely below normal. It also helps to know what kind of low price you are looking at: Flare's guide on mistake fares versus fare drops separates pricing errors from ordinary reductions, because an apparent error may not be honoured the way a deliberate sale is.

Price the whole trip before deciding

A cheap fare can still lead to an expensive trip. Before treating the headline number as the deciding factor, add the costs that come with that specific itinerary:

Treat the fare as one line in a budget. If the total still compares well with your realistic alternatives, you have a much stronger reason to book than the ticket price alone.

• Checked or cabin baggage, if the fare excludes it
• Seat selection, if you need to sit together
• Transfers from secondary or distant airports, especially at late or early hours
• Extra accommodation nights forced by the flight times
• Leave or childcare arrangements tied to the exact dates

Worked example: book now or keep watching?

Example, hypothetical, with invented figures for illustration only. A traveller in Lyon is open to a spring long weekend anywhere in southern Europe. Their own recent searches suggest return fares to Lisbon on suitable dates usually come to around €200. Today they see €130, which is well below their baseline.

They then price the whole trip. The cheap fare excludes a checked bag (€30) and lands near midnight, which means a taxi rather than public transport (€35). Their adjusted total is about €195. A typical €200 fare with daytime arrival and a bag included in a comparable way would have come to roughly €230. There is still a saving, but it is smaller than the headline suggested. The dates fit and their passport is valid well beyond the trip, so booking is reasonable once the price is confirmed at checkout.

If the extras had wiped out the gap, keeping watch or picking another destination would have been just as sensible. Waiting has its own cost, though. The fare could rise or disappear, and nobody can reliably say which way it will move. The decision rests on whether this offer is good enough for you now, not on predicting the market.

Confirm the fare before you pay

A price on a deal page or comparison tool is a snapshot. Fares and seat availability can change between the moment you spot them and the moment you book. The booking provider's checkout is the only place to confirm the final price and availability, and Flare's own guidance is to confirm any fare it shows with the provider before relying on it.

Before paying, read the fare conditions: change and refund rules, what baggage is included, and how names must match your travel document. If an offer looks like a pricing error, hold off on non-refundable hotels or tours until you have a ticket number and confirmation from the seller, whether that is the airline or the agency you booked through.

Check entry rules before booking, not after

A cheap fare is of little use if you cannot board or enter the destination. Passport validity, visa needs and health requirements depend on your nationality and where you are going, and they can change. Check current official sources, such as government travel advice and the destination's embassy or consulate, before you book and again before you leave.

Flare's role is fare discovery, so its guidance covers recognising and confirming deals. It does not cover deciding whether you meet entry conditions. Keeping those two checks separate is a simple way to avoid a cheap ticket becoming a costly mistake.