The following is the third and final part of an extract from the memoirs of Dr. J. A. Pierce who was deeply involved in the development of radionavigation aids in the USA between 1941 and 1973. These are, of course, personal reminiscences, and some issues might be challenged by others working in the same field at the time. However, they give a remarkable insight into the problems faced by the scientists of the day and how they were overcome. This final part deals almost exclusively with the development of the Omega Navigation System, which was the first truly ‘global’ navigation system to enter service. The editing principle used here has been to preserve Dr. Pierces' own wording while eliminating those parts of a purely personal nature. The entire original document without cuts may be found on www.internationalnavigation.org