RUNNER-UP: FareCompare.com
It receives fare data from the airlines for flights within, to, and from the United States and Canada, and then posts the prices several hours before they appear on travel agency sites—and sometimes even the airlines' own sites. Set up a "My Trips" account for alerts on pricing trends and the best dates to book.

AIRLINE REVIEWS
WINNER: Skytrax

WHEN TO USE IT
Before booking an unfamiliar airline.

WHY WE LIKE IT: A must for aviation geeks and infrequent fliers alike, Skytrax offers user reviews of 560 airports and 545 airlines. The site also evaluates service based on analysis by audit specialists. The seat pitch index alone is worth the visit.

TIP: Read the "Seat Reviews" before choosing your next window or aisle seat.

RUNNER-UP: SeatGuru.com
All you need to know about seat comfort on nearly every major carrier.

AIRPORT AND FLIGHT INFORMATION
WINNER: Federal Aviation Administration

WHEN TO USE IT: Before you leave for the airport.

WHY WE LIKE IT: It tells you about delays that the airlines won't. The FAA's Air Traffic Control System Command Center (fly.faa.gov) is the definitive source for flight-delay information.

TIP: For further information, use the hot links to the domestic airline sites.

RUNNERS-UP
Flightstats.com
It allows you to monitor airline punctuality and supplies timely updates.

Security Checkpoint Wait Times
The site provides historical records for every screening point at every commercial airport in the United States.

DOT's Aviation Consumer Protection Division
It offers monthly reports on flight delays and cancellations, complaints, mishandled baggage (including pets), and overbookings.

BOOKING FLIGHTS IN EUROPE
WINNER: Wegolo.com

WHEN TO USE IT: To find great deals on short hops within Europe.

WHY WE LIKE IT: This deep database of low-cost carriers (Ryanair, easyJet, etc.) translates into bargains not always found on other sites. Wegolo searches 75 budget airlines for rock-bottom fares between European cities. Most Americans will feel comfortable on this easy-to-use site: The English-language version features straightforward booking tools and the option of rates in U.S. dollars. On the heavily trafficked London–Paris route, Wegolo had the lowest fare among seven sites for an itinerary one month in advance. That $160 round-trip fare on easyJet was $17 lower than what Kayak posted (ironically enough, for a rate through Wegolo). For a round-trip booking 90 days in advance between Brussels and Madrid, Wegolo's fare of $115 was $42 lower than most of its competitors.