Flight departments are corporate-owned operators who manage the aircraft of a specific company. Ford Motor Company, Chrysler, and Altria are examples of companies that own, maintain and operate their own fleet of private aircraft for their employees. Flight departments handle all aspects of aircraft operation and maintenance. In the United States, flight-department aircraft operate under FAR 91 operating rules.
The key words here are prop planes, turboplanes, and light jets. Prop planes like the Cessna Caravan are popular because they're roomy (the seats are like business class, and often configured face to face). More popular these days are planes like the six- to eight-seater Pilatus PC-12, and KingAirs, which fly faster and feel more like jets. And then you get into light jets like Learjets, Embraer Phenom 300s, and Citation CJ3s, and Hawkers, all of which are sleeker and more streamlined, and can fly for four to five hours, for slightly longer trips.
A single-entity charter is one in which an individual or company charters a plane and bears the entire cost of the flight, so that the passengers do not pay their own airfare. There is no minimum passenger requirement, since the cost is per flight, not per person. Single-entity charters are typically used for business purposes -- for example, travel to meetings and conferences, incentive travel or VIP leisure travel.
In October 2017 Jetcraft forecasts 8,349 unit deliveries in the next decade for $252 billion, a 30.2 $M average. Cessna should lead the numbers with 27.3% of the deliveries ahead of Bombardier with 20.9% while Gulfstream would almost lead the revenue market share with 27.8% trailing Bombardier with 29.2%. For 2016-2025, Jetcraft forecasted Pratt & Whitney Canada should be the first engine supplier with 30% of the $24B revenue, in front of the current leader Rolls-Royce at 25%. Honeywell will hold 45% of the avionics $16B revenue ahead of Rockwell Collins with 37% and Garmin.