Florida (or, probably more specifically, Orlando) remains very popular with UK holidaymakers although the figures are quite confusing with some sources indicating a slow long term decline with others suggesting a recent rise in visitors. There's some evidence that the recent favourable exchange rate is having a positive impact on visitor numbers to the US as a whole.

Which are the airlines you are referring to? I'm seeeing available seats on all the usual carriers for the Easter period although, as usual, it is a very popular time to visit because of school holidays.