Here's a Department of Transportation website that contains that data. Click on departures and fill in the appropriate info:

http://www.bts.gov/xml/ontimesummary.../src/index.xml

Note that data is significantly delayed. Right now, only data from September 2010 and before is available. Also, only certain airlines report data--has to do with their size. I think most Delta Connection carriers are listed.

Hope you find your flight!