A good web site to check the ontime record is

http://www.flightstats.com/

For example, when you fly between Beijing and San Francisco, you definitely want to avoid Air China - they have 4% on time record, and over 70% excessive delay. On the same route, the UA has over 70% on time record.

It will be very stressful and annoying if you had to wait for 10-20 hours on a 12 hour international flight without being taken good care of by the airline.

This web site describes additional malpractice of Air China, the only Chinese airline that bears their national flag.

http://www.ca985.org/

I was wondering if many international travel members here on flyertalk take Air China or not.