Mr. J. B. Parker, in his review of Sight Reduction Tables for Air Navigation, published on pages 98–103 of Vol. VII of this Journal, states that the time required by him to resolve a three-star fix by means of A.P. 3270 is 10 minutes (p. 100). He comments on the ‘errors due to the plotted fix being a hundred or more miles behind the aircraft's position’ (p. 101). Later he says: ‘An accuracy of sight reduction of anything better than certainly 5 minutes of arc, and more logically 10 minutes of arc, will therefore be wasted on a navigator flying with present-day instruments in a fast modern aircraft in high latitudes’ (p. 102).