I don't believe there's an official curfew, but MSY has long been the subject of complaints from residents who live immediately north and east of the airfield. The 1982 crash of Pan Am 759 in a neighborhood just east of the airport didn't help. Google Maps shows that there are still many homes directly in line with the runways to the north and east. (The west is a swamp; the south mostly industrial until the Mississippi River.)

Regularly scheduled late night flights would almost certainly result in complaints from nearby residents.