Which is the cheapest airfare site?

There is no permanently cheapest site. On any given route the low price sits with whichever agency is discounting that week, which is why metasearch exists.

Why the answer keeps changing

Agencies buy inventory on different terms and discount different routes to win volume. The result is that the cheapest seller of a Lisbon flight in March is not the cheapest seller of a Bangkok flight in November. Any article naming one permanent winner is describing a snapshot.

What is stable is the structure. Metasearch shows you many sellers at once, so it finds the low price. Agencies sell, so they show you their price. Start with the first kind.

Where the low fare usually hides

Three places, in order of how often they pay off. First, a day either side of your dates. Second, a nearby airport. Third, an airline that does not distribute widely, which means checking a budget carrier's own site.

A fourth, less often: booking the outbound and return with different airlines as two one-ways. Metasearch will build these for you automatically and label them, and on short-haul they are regularly the cheapest option on the page.

Compare the same ticket

A fare that is 40 dollars cheaper and excludes a carry-on is not cheaper. Before you decide which site won, put both fares on the same footing: bag, seat, and what happens if you need to change it.

Common questions

Which site has the cheapest flights?

Whichever one is discounting your route this week. Search on Google Flights and one of Kayak, Skyscanner or Momondo, and the low price will be on one of them.

Are budget airlines included in flight search results?

Not always. Several sell only through their own websites, so check the obvious budget carrier on your route directly before you book.