An aircraft must travel __________ at 10,000ft than at 1,000ft.

At higher altitudes, such as 10,000 feet compared to lower altitudes like 1,000 feet, aircraft are generally able to fly faster. This phenomenon occurs due to several factors, including reduced air density and drag at higher altitudes. As an aircraft ascends, the air becomes thinner, which means there is less resistance against the aircraft's surface, allowing it to travel at higher speeds more efficiently.

Additionally, engines tend to operate better at higher altitudes where the temperature is lower, resulting in more efficient thrust. This capability is essential for aircraft designed for cruising at altitude, as they can cover greater distances more quickly. Therefore, the correct assertion is that an aircraft must travel faster at 10,000 feet than at 1,000 feet.