Look it up on Flightaware.com. Put in DAL184 in top left box for flight number, and then scroll down and look at the flights each night from JFK to CDG (there is an aircraft change from Portland to JFK, a 73N, and then onto CDG). It says every other night in the last month has been a 767-300. Why would it be a 747-400 tonight ONLY? Maybe they expect more passengers tomorrow. If it were a charter, it would have 4 digits like 9939. Pretty smart, eh?