Click here > http://matrix.itasoftware.com/cvg/dispatch/
Click “Month Long Search”
Click either One Way, or Round Trip. (See thread at top of Cheap Flights forum on Visa Entry Requirements especially if considering one-way). It can do multi-city, but only when you choose the Specific Dates option. This also allows you to check +/- 1 day. A round trip search with multiple cities input sometimes turns up a multi-city result—keep reading for that….
Type either city name or airport code in the From and To boxes. You can search several at the same time if you connect them with no spaces and semicolon. For example from Sioux Falls;Boise;Cedar Rapids to: Munich;London;Brussels;Kiev Likewise, if you know airport codes you could do from FSD;BOI;CID to MUC;LON;BRU;IEV. The more you stack, the greater the chance it might miss a (good) fare combination, so don’t over-do it. They do not need to be capitalized.
Choose your start date—the absolute earliest date you could consider departure—and your length of stay.
Note: ITA does not do bookings! They search fare combinations that standard flight searches don’t always find, and make fare fluctuations over a month-long window very obvious.
To book, try the exact same dates and cities with 1) the airline(s), 2) Orbitz, 3) other booking engines—Kayak or Cfares if it’s a multi-city itinerary; BookingBuddy and consolidators listed in our New User Thread (top of Cheap Flights forum) if it’s a simple round trip.
Note that ITA sometimes finds stuff that just does not turn up elsewhere. This could be due to human error on fare data submitted to them by airlines, or seats sold out since latest availability update, or sometimes airlines just not allocating seats on a fare that they have filed.
ITA also shows code shares that might be cheaper to book. Code share= book a ticket from Airline A, actually fly it on their partner Airline B. For example, recently I’ve noticed KLM cheaper on some transatlantic flights to places that I know KLM does not fly to (KLM’s hub is AMS), but they’re cheaper to buy from KLM even though you’ll actually fly on Delta.
ITA does not require membership or software downloads to use it’s free search.