· FlightAware


The site is easy to use if you have some specific information, such as the name of an airport or airline and a flight number. The maps are easy to read and decipher. Expect a harder time if you don't know the flight number. By registering on the site for free, you can examine the on-time performance of a flight each day over a month. The site doesn't synthesize that information in a chart or graph. However, it does provide real-time graphics that show air traffic at airports.

· FlightView


Generally works the same way as FlightAware. But its maps are not as large or easy to read. Even without a flight number, visitors can track flights between cities and can use a service that provides a constantly updated map depicting a plane's flight path.

· Flight Explorer


Offers a succinct graph that explains departure and arrival delays at any domestic airport. The site also offers users the ability to track flights in 3-D.

· FlightStats


Provides a wealth of data for those interested in historical information about on-time performance. You can even learn which flights between two cities have the fewest delays. FlightStats also provides gate numbers for flights, but it is always a good idea to confirm that information with airlines because it can change.