With the comparative absence of navigation aids in the earlier days of flying, up to about ten years ago, the navigator was constantly engaged in associating observations, calculations and chart work in what was essentially a high-class guessing game. The low speeds (just over 100 knots on flying boats and just under 200 knots on landplanes) provided enough time for this rather intriguing exercise to be carried out in a fairly relaxed atmosphere, conducive to an individualistic approach that could be justified by results. The navigator's performance was largely (at that stage of aviation) judged on the neatness of his plotting, the accuracy of E.T.A.'s and the absence of late course corrections before arriving at destination or a check point. If there is anything in the view that navigation is an art, this particular yardstick certainly induced considerable artifice in the navigator.