What does a 'W' followed by a number indicate on an airspace chart?

A 'W' followed by a number on an airspace chart indicates Warning Areas. These areas are established over international waters and are designed to warn non-participating aircraft of the potential hazards associated with military activities. The purpose of warning areas is to notify pilots of the active operations occurring within these zones, where there may be live ordnance exercises or other potentially dangerous activities. The number following the 'W' serves as a unique identifier for the specific warning area.

In summary, warning areas are essential for maintaining safety in airspace where military training and exercises take place, allowing civilian pilots to avoid those areas when they are active. Understanding this designation is crucial for both operational safety and regulatory compliance in aviation.