The two best sources for this type of data are FlightAware and Flight Stats. Although these sites both get data from the FAA, I don't know that either would be considered "official".
The nearest to official source would be the FAA data available at http://www.bts.gov/xml/ontimesummarystatistics/src/index.xml however this data is always several months behind (eg, they currently have up to November 2011), and not as easy to search for specific flights as either of the above two sites.
For (at least) Flight Stats you'll need to create an account to look at historic data, however it's free to do so.