Answer: "Within aircraft range of Brazil" means that a location or object is situated close enough to Brazil so that aircraft can travel to or from it without refueling. This is a distance that can be covered by aircraft without requiring additional fuel or making stops along the way. The phrase is often used in a military context to describe a location that can be reached by aircraft for the purposes of military operations or reconnaissance. It can also be used in a civilian context to describe a location that is easily accessible by air travel from Brazil, such as a nearby island or coastal city.
Explanation: In this passage, "within aircraft range of Brazil" means that Dakar, a city in West Africa, is close enough to Brazil so that it is possible for aircraft to travel to Dakar from Brazil without refueling. The passage suggests that American officials were concerned about the possibility of an attack on Dakar from the southwest, possibly by German forces. The proximity of Dakar to Brazil made it a potential target, and American officials were sensitive to this because of the strategic importance of Dakar as a port and a gateway to West Africa. The passage also mentions Hitler's desire to capture Gibraltar, which was another strategic location that was of interest to both Germany and Britain during World War II.