The answer to the crossword for the term 'PILOTS' GUESSTIMATES: ABBR.' is ETAS, which stands for Estimated Time of Arrival. Pilots' guesstimates are estimates made by pilots of the time of arrival at a destination. These estimates are based on factors such as the aircraft's speed, wind speed, and other environmental conditions. ETAS is used to help pilots plan their flights and ensure they arrive at their destination on time.