What is used for expressing headings in aviation, when appropriate?

In aviation, headings are crucial for navigation and are typically expressed in relation to magnetic north. This means that the headings are measured in degrees magnetic, which aligns with the Earth’s magnetic field. Pilots utilize this reference to effectively navigate and ensure they are on the correct flight path. Magnetic headings are especially important when flying under instrument conditions or during precise navigation maneuvers, as they help pilots avoid conflicts with terrain and other aircraft.

Using degrees true, although it can be relevant in some contexts, relates to the geographic north pole rather than magnetic north and requires additional conversion to maintain appropriate heading during flight. Degree decimal typically refers to coordinates rather than headings, and altitude readings pertain to vertical positions, not directional headings. Hence, degrees magnetic is the standard expression for headings in aviation, making it the correct answer.