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 https://transtats.bts.gov/ONTIME/. However, this data is always several months behind (eg, they currently have up to June 2019 as of August 2019), and not as easy to search for specific flights as either of the above two sites.
For both Flight Stats and FlightAware, you'll need to create an account and buy a subscription, unless the data you want is only a few days old.