For travelers to Belize who would like to arrive via Cancun, check out these air carriers:
MLT Vacations - Champion Air flys from Dallas, Denver, Minneapolis and St. Louis.
Spirit Airlines - Fort Lauderdale is their international hub. They fly from Atlanta, Atlantic City, Boston, Chicago, Detroit, Fort Lauderdale, Las Vegas, Los Angeles, Myrtle Beach, New ork La Guardia, Orlando, Tampa, Washington DC Reagan National. I know from personal experience that on Saturdays you can get a direct flight from Cancun to Detroit.
Northwest Airlines has last minute seat sales. I have flown for $170 one way and $270 round trip from Cancun to Detroit.
American Airlines has last minute seat sales and I have flown for $250 round trip last year in September
My favorite was
USA 3000 (which no longer flys from Detroit) I could often fly for $99 one way, the planes were nice and the stewardesses were not surly. They fly from Baltimore, Chicago, Cincinatti, Cleveland, Columbus Ohio, Philadelphia, Pittsburgh, St. Louis.
I have pretty much ruled out cheap airfare (under $500) to Detroit as being a possibility from Belize and for many many years have made the trek up to Cancun. I always allowed $200 extra in my budget for additional traveling expenses and never paid more than $300 for a round trip ticket, sometimes my tickets were as low as $225 round trip. Now that I have my studio in Chetumal, Mexico, I allow $35 each way to get to and from Chet to the airport in Cancun, and I don't overnight it in Playa Del Carmen. When I fly out of Cancun I choose late afternoon flights so I can take the bus or drive up in the morning to not pay for a hotel overnight.
You have to haunt these websites, checking at least once a week for sales and hot deals and sign up for their email newsletters. You have to be very flexible on your fly dates and sometimes I buy my airfare and fly 2 days later if the price is right. The cheapest months to travel were May, September and October. I always book online. You also have to be aware that you won't get the frills of full prices carriers. The planes are sometimes dirty, the stewardesses surly, you can't even get a free glass of water and the seats are cramped. I'll admit it, I'm cheap and I'm willing to be inconvenienced for a couple of hours to save hundreds on airfare. I also have to admit that I would rather take the bus down from Cancun than to pay for a flight on Maya unless the price was ridiculously low. So call me cheap, I already know it.