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Before booking airplane travel, I visit a bunch of Web sites for a 30,000-foot view of available flights, rates, and other particulars. Here are some sites I recommend for frequent fliers.

Farecast

Farecast is my first stop, because it charts where airfares for a particular itinerary have been in recent months and predicts what they're likely to be in the near future. (PC World named Farecast one of the 20 most innovative products of 2006.)

For instance, let's say you want to travel from San Francisco to Honolulu, and getting a great fare is more important than when you actually travel. When you enter those cities as your originating and destination points, Farecast will show you on a graph what the airfares for that trip were in the past 81 days. Another graph shows you what the airfares will likely be in the next two months, based on historical data and trends. Using Farecast, I discovered that the San Francisco to Honolulu trip would likely cost between $364 and $742 round-trip, depending on when I booked. Currently, Farecast predictions are limited to about 75 U.S. cities.

Like Kayak (see below), Farecast doesn't allow you to make reservations, but connects you to sites that will. Instead, both sites search other travel sites and provide results that are easily adjustable using slider bars or by unchecking airlines and airports. For example, if you don't like to fly US Airways (and I'm not a fan), just remove the airline's check mark from the list of carriers; both sites will update your search results without US Airways.

Kayak

Unlike Farecast, Kayak, one of PC World's 100 Best Products of 2007, also lets you search for hotels, rental cars, and cruises. And Kayak's Buzz section reveals the best prices other Kayakers have found for top destinations in the past 48 hours.

ITA Software

ITA Software is another good option for finding the lowest airfares. Founded by MIT scientists, ITA Software is a search engine that's known for not favoring particular airlines (unlike some travel planning sites). And it provides a convenient way to find itineraries that combine the lowest fares with the most convenient routing.

Yapta

Ever worried that the airfare for an itinerary will drop after you've booked a nonrefundable ticket? Me too. That's where the recently launched Yapta comes in.

While some sites, such as Travelocity's Fare Alert, notify you of fare decreases between two cities, they don't alert you when a rate for a specified itinerary changes. Yapta does. Once you've settled on or booked your trip, register with Yapta to receive e-mail alerts whenever the fare for that specific itinerary drops. Why does it matter, you ask? Because many airlines will refund or credit the difference between the fare you paid and the new, lower fare, though you may be hit with a change fee. (At least, that's the current situation; if Yapta becomes a runaway success, it's possible some airlines may change their policies.)

Yapta works in two ways. You can download and install the free Tagger applet, which lets you automatically tell Yapta to start tracking an itinerary you've planned on a variety of travel sites. Or you can manually enter itineraries directly on the Yapta site. Currently, the Tagger applet only works with Internet Explorer. Support for Tagger in Mozilla Firefox is imminent, according to Yapta. In the meantime, Firefox users can manually enter itineraries at the Yapta site. Another limitation: Yapta doesn't currently track a multi-airline itinerary, though you can track each flight segment individually.

A Few More To Go

• FlightStats lets you view on-time performance records of major airlines.
• SeatGuru provides seating diagrams for many domestic and international aircraft. Always check out your seats here before you book.
• MileageManager charges $15 yearly to track all your airline, hotel, and rental car membership points, and sends you updated e-mail summaries. Unfortunately it doesn't tell you when your points expire, however.
• WebFlyer is a useful tool for comparing one frequent flier program to another, checking blackout dates, converting miles from one program to another, and a lot more.

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Contributing Editor James A. Martin offers tools, tips, and product recommendations to help you make the most of computing on the go. Martin is also author of the Traveler 2.0 blog. Sign up to have the Mobile Computing Newsletter e-mailed to you each week.