I've noticed that Fuerteventura seems to have less charter flights than the other main Canary Islands (Tenerife, Arrecife and Las Palmas). I've also heard that there is a restriction which means flights cannot depart Fuerteventura after midnight. Is this a reason for the lower amount of flights to the Island, seeing as, depending on the day, a lot of flights from the other three main islands depart between 0000-0400. With Fuerteventura, these departures are not possible.
I myself have been to Fuerteventura, twice in fact (although once was only for 4hrs when i got a ferry - Fred Olsen - from Lanzarote). I must admit where i went seemed a little unbuilt, so maybe this is why there are less flights.