What is the Design Aircraft defined as?

The correct answer is the most demanding aircraft with frequent use. In the context of airport design, the Design Aircraft refers to the aircraft that represents the operational demands placed on an airport's infrastructure. This includes factors such as size, weight, wingspan, and operational requirements like frequency of use. The Design Aircraft is typically the one that, while it may not be the largest aircraft to use the airport, imposes the most significant design criteria due to its operational profile.

This consideration ensures that the airport can accommodate the highest anticipated levels of activity, safety standards, and operational efficiency associated with frequent usage. By focusing on the most demanding aircraft, airports can ensure their facilities are adequately prepared for typical operations catered to their users.

The other options, while related to aircraft operations, do not capture the key concept of Design Aircraft in airport planning, which revolves around operational frequency and demands rather than size or delays.