Here is the latest (Feb 2000) DOT data on cancelled flights by the top 10 USA airlines. Southwest and Continental have the lowest percent of flights cancelled.

Unfortunately Alaska cancelled about 1 in 12 flights and AmericaWest and United cancelled 5.8% and 5.3% respectively. Ugh!!

http://airtravel.about.com/travel/ai...s/blfebxld.htm