I'm guessing general spring break travel demand for MSY. Very limited coach companion cert availability from about mid-March through the end of April (just spent some time with the calendar and playing with weekend dates). Pretty decent availability outside of that band (including though-out the summer). Availability is generally better if you can return on a Monday instead of a Sunday. Suspect that MSY suffers from Vegas-like travel patterns (everyone wants to go for the weekend and return Sunday afternoon) and the airlines are obviously aware of that.