Aerospace medicine encompasses "aviation medicine," "space medicine," or both. Aviation medicine refers to the condition and needs of pilots and passengers flying in the atmosphere, space medicine to those in Earth orbit or beyond. The term "aerospace" is sometimes used to describe flight that blurs the boundaries between ordinary aircraft and spaceship. For example, a high-performance jet aircraft might operate at several times the speed of sound, fly to altitudes near the edge of the atmosphere, or maneuver in a way that exposes the plane's occupants to high g-forces. Medically, this combines challenges of both aviation medicine and space medicine.

          There are several aspects to aerospace medicine, involving the human subject, the machine, and the environment in which they will operate. A primary job is screening individuals who are looking for employment in aviation or space flight for susceptibility to environmental and work conditions that are part of the job. For example, someone with limited vision or hearing, a hidden heart condition, respiratory problems, or who is subject to vertigo or motion sickness would have problems piloting an aircraft safely and comfortably and dealing physically with the stresses of acceleration and deceleration or the lack of oxygen in the upper atmosphere. Other practitioners work on developing instrumentation to better measure the physical abilities of the test subject and the stresses imposed on the body. These would include devices to measure color vision, hearing at various frequencies, reaction to temperature changes, and many other physiological conditions. Still other aeromedical specialists interact with the vehicle designers in what is called "human factors" engineering, making the human - machine interface more functional, effective, safe, and user-friendly. This can include everything from finding the range of head sizes needed to put a helmet on every pilot in the Air Force to choosing the optimal cockpit layout for a pilot trying to manipulate controls while pulling three or four g's. A final group works with scientists and engineers who evaluate the physical environment and decide what is needed to allow a human being to live and work under those conditions. They study issues like radiation exposure, weightlessness and bone loss, cold at high altitudes, the body's tendency to form blood clots at high altitudes, and more.