EAL flew the A300 on a service called the "Moonlight Special" during the mid-80s from IAH and MCI to points on the east and west coast. If they flew the A300 into MSY then more than likely it was via IAH on this service. I -had- a 1982 schedule from EAL but it's long gone (also had a Braniff one-right before the bankruptcy at that!)
The Moonlight Special flew late at night. Low fare, pay to check your bags. Flew from LAX/SFO Possibly SEA? to MCI and to IAH. Onwards to EWR, BOS, PHL (I think) ATL, MIA, IAD?. The trick to making it work was EAL had a considerable US postal service contract that filled up the bellies of the A300s with mail. Mail would be moved just in time for delivery the next day. Sounded like a great idea, considering this was before FedEx was as big as it is now and UPS was just getting to be a serious overnight transcon cargo mover as well. The little space that was left over in the A300 bellies was at a premium and you had to be charged to check your bag, but the ticket price was dirt-cheap. It lasted for a year or so, then faded away. It was right around the time the MCI hub was shutdown that the "special" went away I think.
So, back then you more than likely flew on a 727-100/200 or DC-9-31/51. Their heavier stuff was generally out of ATL/MIA and the New York/Boston market. The 757s didnt start delivery until '83. I sincerely miss that airline.