Final answer:
The heading of the airplane remains northwest (NW) throughout its journey.
Step-by-step explanation:
To determine the heading of the airplane after adjusting its course, we need to consider the initial heading and the change in direction.
Let's assume that the initial heading is northwest (NW).
After traveling 320 miles, the airplane adjusts its course to northwest (NW) again, meaning there is no change in direction.
Therefore, the heading of the airplane remains northwest (NW) throughout its journey.