Pilot's Guesses is a term used in aviation to describe the process of estimating the position of an aircraft based on the pilot's experience and knowledge. It is a form of dead reckoning, which is the process of calculating one's current position based on a previously determined position. Pilot's Guesses are used when other navigational aids, such as GPS, are not available or are unreliable. The acronym ETAS stands for Estimated Time of Arrival and is used to calculate the estimated time of arrival at a destination.