The average traveller books a flight in about 20 minutes, clicks the cheapest fare on the screen, and moves on. That speed is exactly what airlines count on. Between basic economy restrictions, baggage fees, seat charges, and change penalties, the cheapest fare on the search results page is often hundreds of dollars more expensive by the time you reach the gate. The good news is that nearly every one of these costs is avoidable with a few minutes of attention at booking time. Here are the seven mistakes that cost travellers the most money, and the simple habits that prevent them.

Basic economy is the single biggest source of surprise charges in air travel. The fare looks $40 to $80 cheaper than standard economy, but it often excludes a full-size carry-on, seat selection, changes, and refunds. On some US airlines, basic economy passengers board last and cannot choose a seat, which means families get split across the cabin. On international routes, the difference can be steeper: some basic fares do not include checked baggage at all. Before you book, compare the total cost, not the headline fare. Add the checked bag fee, the seat selection fee, and the change fee if your plans might shift. In many cases the standard economy fare is cheaper once everything is included, and it is always more flexible.

A 45-minute connection looks fine on a booking site, but it leaves no room for a late arrival, a gate change, or a slow deplaning process. If you miss the connection, the airline will rebook you, but you may lose a day of your trip. The safe minimum is 60 minutes for a domestic connection and 90 minutes for an international one, and two hours is wiser at large hubs such as Heathrow, Frankfurt, or Istanbul. Also check whether the connection requires changing terminals or going through security again, which can add 30 to 45 minutes. On the other hand, a very long layover is not free either: a six-hour wait can cost $30 to $50 in food and drinks. Aim for the sweet spot of 90 minutes to two hours.

Airlines charge significantly more for checked bags at the airport than online. A bag that costs $35 when added during booking can cost $60 or more at the check-in desk, and $100 at the gate. Budget airlines are the worst offenders, with some charging more for a bag at the gate than the ticket itself cost. The fix is simple: decide on bags before you book, add them during the booking process, and weigh your suitcase at home. A portable luggage scale costs under $15 and pays for itself the first time it saves you an overweight fee, which typically runs $100 to $200 per bag. Also check the carry-on size and weight limits for your specific airline, because they vary widely and enforcement has tightened in 2026.

Flight prices change constantly, but a few patterns hold. Flying on Tuesday or Wednesday is usually 10 to 20 percent cheaper than flying on Friday or Sunday, and early morning departures are often the cheapest of the day. Booking six to eight weeks ahead is the sweet spot for most international routes; booking too early or too late both cost more. Use price tracking tools such as Google Flights to watch a route and get alerts when the price drops. Clear your cookies or use a private browsing window when searching, because repeated searches for the same route can push prices up on some booking sites. Finally, always check the airline's own website before booking through a third party: the airline often matches the price and gives you better change and refund options.

Is basic economy ever worth it? Yes, for a short solo trip with only a personal item and fixed plans. For families or trips with bags, usually not. How far in advance should I book international flights? Six to eight weeks is the typical sweet spot, though popular holiday routes need earlier booking. Should I book directly with the airline? Usually yes. Direct bookings are easier to change and refund, and the price is often the same. What is the minimum safe layover? Sixty minutes domestic and 90 minutes international, longer at large hubs. Do flight prices really rise when I search repeatedly? Some booking sites use dynamic pricing, so use private browsing and price alerts to be safe.