What does the 'D' in the weather deviation entry represent?

The 'D' in the weather deviation entry specifically refers to 'Deviation from filed route.' This indicates that an aircraft has altered its course from the original flight plan due to weather-related issues. When pilots encounter adverse weather conditions, such as turbulence, thunderstorms, or significant cloud cover, they may need to adjust their flight path to ensure safety and comfort. The entry ensures that air traffic control and other relevant entities are aware of these deviations, facilitating better coordination and safety in the airspace. This is crucial for maintaining situational awareness and ensuring that all parties involved are informed about changes to the aircraft's intended route due to weather factors.