By visiting the section they call "Causes of Delays", you can get nice pie charts showing the percentages of flights for each airport, airline, or combination thereof that were:

• on time
  
• delayed (at least 15 minutes) due to the airline
  
• delayed due to the plane arriving late
  
• delayed due to weather
  
• delayed due to security issues
  
• delayed due to the "national aviation system"
  
• cancelled
  

This information allows you to compare the track records of specific airlines and airports before purchasing tickets. Above are pie charts that compare Southwest versus US Airways departing from Washington Dulles.

So far in 2007, 81% of Southwest flights out of Dulles have left on time versus 57% of US Airways flights. I know which airline I would prefer to book a flight on!

A somewhat hidden feature is the ability to get the percent of on-time flights versus any dimension in the database. This means you can see how many flights were on time by:

• Unique Carrier
  
  (I will spare you the suspense [2007 year-to-date]):
  
  • 93.03% — Hawaiian Airlines Inc.
    
  • 91.12% — Aloha Airlines Inc.
    
  • 80.66% — Southwest Airlines Co.
    
  • 78.20% — Delta Air Lines Inc.
    
  • 78.15% — AirTran Airways Corporation
    
  • 77.45% — Frontier Airlines Inc.
    
  • 77.29% — Pinnacle Airlines Inc.
    
  • 74.80% — Skywest Airlines Inc.
    
  • 73.74% — Alaska Airlines Inc.
    
  • 72.58% — Continental Air Lines Inc.
    
  • 71.71% — Expressjet Airlines Inc.
    
  • 71.50% — Mesa Airlines Inc.
    
  • 70.86% — United Air Lines Inc.
    
  • 68.28% — Northwest Airlines Inc
    
  • 68.08% — American Eagle Airlines Inc.
    
  • 67.18% — American Airlines Inc.
    
  • 67.18% — Atlantic Southeast Airlines
    
  • 66.20% — JetBlue Airwcys
    
  • 66.12% — Comair Inc.
    
  • 63.36% — US Airways Inc.
    
  
  
• Day of Week
  
• Origin Airport
  
• For more dimensions, click the "analysis" link on the right of the dimension you want to see.
  

Finally, if you are a data guru, then you can also download the entire database or any subset that you like.

I am obviously a fan of the airline information from BTS, and I have only scraped the surface of the agency's airline information.

However, I have two suggestions for the BTS web team. (1) Increase the font size for the Cause of Delay pie chart legends; they are hard to read even with my 20/20 vision. (2) Consider providing and promoting information that supports the task of comparing on-time track records between airlines, airports, and day of week when purchasing tickets. For example, allow users to get Cause of Delay pie charts for all airlines at a given airport or for several airlines at two different airports. It is this head-to-head comparison of airlines and flight options that travelers need to avoid travel delays.

I emailed this article to BTS via answers@bts.gov and invited comments.