In what situation might a compass accurately indicate heading during flight?

The compass accurately indicates heading during straight-and-level unaccelerated flight due to the stability and lack of external forces acting on it. In this condition, the aircraft maintains a constant altitude and direction, allowing the magnetic compass to function as designed. The compass relies on Earth’s magnetic field, and when in straight-and-level flight, the aircraft is not experiencing significant banking, acceleration, or turns, all of which can introduce errors in the compass reading.

In contrast, during steep turns, the compass can be influenced by the angle of bank, leading to an apparent turn indication even when the aircraft is not changing its heading. Transitioning between altitudes could involve vertical maneuvers which may also confuse the compass readings, and while taxiing, the compass might not provide a reliable heading indicator due to the low speed and potential magnetic interference from the ground or structures nearby.