Final answer:
The appropriate altitude for cruising flight in the Northern Domestic Airspace is guided by the aircraft's True track, which is a navigation factor. Engine power, speed, and fuel efficiency affect flight performance but do not determine cruising altitude in this context.
Step-by-step explanation:
The determination of the appropriate altitude for cruising flight in the Northern Domestic Airspace is based on the aircraft's True track. Factors such as engine power, maximum speed, and fuel efficiency are certainly important to various aspects of flight performance, but the directional guideline for altitude selection, especially in regulated airspace, is oriented around the aircraft's true track, based on aviation rules that specify different altitudes for different directions of flight to enhance safety and navigation efficiency.
Safety and efficiency in cruising flight depend on managing the relationships between air density, lift, and drag. When cruising at high speeds such as 245 m/s, and at an altitude where air density is one-fourth that at sea level, the required airspeed over the wing for lift is affected by these conditions. It's also important to note that while the drag coefficient can be a factor in determining fuel efficiency and optimal cruising speeds, for the specific question at hand, it is the aircraft's true track that guides altitude selection.