Compared to the development of computers, or the Internet, or even cars, the evolution of aviation equipment appears to be very unhurried. Several factors contribute to this very gradual pace, but one of the most important is the extreme care with which any innovation affecting safety has to be examined, evaluated, analyzed, and tested. Satellite navigation equipment for aircraft is not an exception, so predicting its future for the next20 years is relatively easy compared to predictions for other fields.

In this paper first of all we will describe briefly the challenges that satellite navigation must solve to be available solution for aviation. Then, we will describe the systems that have been developed to overcome these challenges and the performance they offer today, or will offer very soon. There is currently an explosion in satellite Navigation: before the end of this decade there will be over three times more satellites, offering civil signals in two distinct frequencies (as opposed to one today).