How long in advance do the airlines have most of their flight times posted? We have always been able to depart MCO in the afternoon but not the only returning flights are around 7am... Not terribly appealing when using magical express Tia
The legacy carriers -- United Airlines, American Airlines, US Airways (which now owns American and will roll itself into American), and Delta Air Lines -- have flights available for 330 days from the current date.
Southwest Airlines has flights available through August 8, 2014.
For smaller airlines, check their websites.
It's not a case of posting "most of their flight times." On the legacy carriers, it's the entire schedule, but the schedule can change. An airline might change equipment, change a flight number, adjust the time (which could mean a few minutes or a few hours). An airline might add a new route, eliminate a route, or adjust frequency (such as changing from 3 flight per day on a route to 2 or 4). Legacy carriers are always looking for opportunities to maximize profitability through schedule changes.
But a legacy carrier that plans to operate 4 flights per day on a given route in December 2014 won't post 2 planned flights now and the other 2 planned flights in July.
Southwest is much better about keeping its schedule firm once it's released. It can do so because flights are only posted around 6 months in advance.
Also, carriers don't cancel a single flight on a single day because bookings are light. If a flight is consistently unprofitable and does not feed passengers to profitable routes, an airline is likely to drop the flight entirely from its schedule. But flights can and do operate with empty seats (although, these days, far more flights are completely full).