Southwest and JetBlue will often let group customers book as many seats on a flight as they wish.
This happens because Southwest and JetBlue have non-refundable deposits, so the financial risk of a group cancelling and then the airline struggling to fill the seats is negligible.
Should you intend on taking all of the seats on a plane, and need special arrival and departure times, you should consider chartering the aircraft. When chartering, airlines will work with you to find a departure time and route that works best for your group.
