What do turbojet airplanes designed for long range need to maintain during cruise flight?

The correct answer highlights that turbojet airplanes designed for long range need to maintain maximum gross weight as fuel during cruise flight. This is crucial for several reasons.

Turbojet engines, particularly in long-range applications, are designed to operate efficiently at high speeds and altitudes. The efficiency of fuel consumption is highly dependent on the weight of the aircraft. In long-range operations, aircraft are typically fueled with maximum fuel load to ensure they can reach their destination without stopping for refueling. The ability to maintain maximum gross weight allows aircraft to achieve the optimal range, which is vital for long-distance travel.

While the configuration, drag, and altitude all play important roles in cruise flight efficiency and performance, the primary focus for long-range turbojet operations is often on ensuring sufficient fuel is onboard to complete the flight without the need for intermediate stops. This aspect directly relates to the design considerations of turbojets, which often need to achieve a delicate balance of weight and fuel efficiency to maximize range capabilities. Thus, for long-range operations, maintaining maximum gross weight as fuel is essential to achieve the necessary operational range and efficiency.