The easiest way to find and compare all of the flight and fare options for a particular route is to use one of the many online travel agencies (which sell tickets) or fare aggregator sites (which direct you to an airline or other website to purchase the fare).
But do any of them offer lower prices than others?
Consumer Reports spent two weeks looking for the cheapest nonstop airfares on five busy domestic routes using nine popular sites — CheapOair, Expedia, Google Flights, Hotwire, Kayak, Orbitz, Priceline, Travelocity and TripAdvisor.
It performed four sets of simultaneous searches on different days at different times, for a total of 372 queries. To check for merchants offering different prices to consumers based on their computer's browser history, it had at least one tester use a browser with a robust history of searching flights (typical of a comparison shopper) and another using a "scrubbed" browser, or one cleared of all of the "cookies," or data files, that record previous web searches.
The average prices overall ranged from $299 for Travelocity to $335 for CheapOair, which delivered the highest average fare and also failed to provide even a single lowest fare among the five routes in the test. And fares varied as much as $138 for the same route at the same time and as much as $238 over different days.
Among the 372 searches, Consumer Reports found 42 pairs of different prices on separate browsers for the same sites retrieved at the same time (in theory, there should have been no differences). In fact, all nine sites provided different fares on separate browsers at the same time at least once, although it occurred most frequently on Google Flights (12) and Kayak (8). Out of the 42 pairs that differed, 25 resulted in higher fares (by as much as $121) and 17 resulted in lower fares (up to $84 less) for the scrubbed browser.
So to increase your chances of finding the lowest fare, search for flights multiple times and over multiple days, both with and without the cookies cleared from your browser.
Other shopping tips
• Cover all the bases. Before booking a fare on an online travel agency such as Expedia or Orbitz, search google.com/flights to see all of the carriers that serve the route you're flying, then check the airlines' own sites to see if you can find an even lower fare.
• Be flexible. Consumer Reports found that fares could vary considerably for flights just hours apart, and at crosstown airports. All of those sites offer filters to help you narrow or broaden such choices, though Kayak's were found to be best.
• Use price alerts. Kayak's, for instance, will email you weekly or even daily notices when the price falls — helpful when you're shopping for fares well in advance.
• Don't stop shopping after you buy a ticket. By law, you can cancel a booking without penalty for 24 hours after you pay for it, as long as you're not traveling for at least a week.
To learn more, visit ConsumerReports.org.