The key modification to the aircraft is the telescope bay and aperture door, which occupies much of the fuselage between the wings and tail. SOFIA also features new high-power engines, state-of-the-art avionics, and a control room where high-flying astronomers will operate the telescope and scientific instruments and where teachers will help prepare the next generation of researchers.
Initial test flights, scheduled to get under way by early 2007, will be conducted with the aperture door closed and will focus on proving the refurbished aircraft's airworthiness. Then, perhaps a year after the first closed-door flight, comes the real nail-biter: the first flight with the telescope exposed to the sky. Aircraft designers have "pushed the envelope" of aerodynamics to ensure that airflow inside the telescope bay will not be turbulent and that the pilots will have no problems handling the plane with the aperture door open. Once they know they've succeeded, they'll turn SOFIA over to the astronomers.