[Butch Cassidy Slept Here]

Regardless of whether the drunk was a Delta employee or not, if he was as obviously drunk as the OP has described he, almost certainly, would exceed the legal blood-alcohol limit for driving in Vermont (and probably most other states.) Accordingly, in a small airport like Burlington, it might have been worthwhile to approach an airport police officer and relay the drunk's statement about driving. Again, in a small airport, someone this plastered might be easy to spot. I wouldn't have too much confidence about making such a report in a large place, like Newark (EWR.) I could see the Port Authority cop say something smart like "what do you want ME to do about it!" Again, the purpose of making such a report would not be all that vindictive, but rather a public safety issue.