Tickets at this price are available on Monday through Thursdays starting in late September through February 13, 2019. Other dates are widely available. Keep in mind this books into American Airlines basic economy fare bucket, but after September 5th a standard carry-on will be allowed with those fares. Checked baggage and seat selection will cost additional and bumping up to regular economy will cost $50 more roundtrip.
Seen below, I found seats departing MIA on Monday, October 8 and returning from BZE on Monday, October 15, 2018.
Have a peek at our other deals departing from Miami on the MIA fare details page here.
Need a hotel while in Belize City? Here's a list of what's available for the selected dates on Hotelwatchdog.