There are substantial differences between airplanes. Pilots learn different airplanes in ground school for the system operations, computer programming, and standard procedures, then use full flight simulators to learn the flight profiles. Initial training (ground school and simulator) is very intense, usually requiring over 4 weeks. Upon successful completion of initial training, a pilot flies with an instructor pilot in regular line flights for several trips until the instructor is satisfied that the trainee is fully ready to fly regular flights.