I believe the scheduled flights for Caye Chapel are on the Maya Island website, //AmbergrisCaye.com/mayaisland/
i seem to remember putting them there! but do not remember the exact cost. also email maya island at firstname.lastname@example.org of tropic airlines at email@example.com.
the flights are just minutes, and also boat transportation would be availbale from the Thunderbolt: //AmbergrisCaye.com/thunderbolt/