This book concentrates on the aviation industry and is essentially commercial in content. It therefore seems appropriate that this chapter follows suit. While being, to many eyes, intrinsically valuable in its own right, a civil transport aircraft, or airliner, only has value to the industry it serves if it does its job well. This is to fly as much payload as quickly, as far and as efficiently as possible. Thus the developments in aviation covered in this chapter, while all possessing admirable technological virtues, will be primarily considered in relation to the above goal.