Recent papers on the future of astronomical navigation in the air indicate that the present trend of development is directed towards surmounting two principal obstacles: the time lag between the shots and the final fix, and inaccuracies due to accelerations of the bubble. Even in aircraft at speeds between 200–300 m.p.h. these two factors tend to discourage the use of astro-navigation even where, as is particularly the case in lower latitudes, radio aids are not available.