What is considered 'substantial use'?

• A. Largest Plane With 1,000 Annual Itinerant Operations
• B. Small General Aviation Aircraft
• C. Largest Plane With 500 Annual Itinerant Operations
• D. Any Commercial Service Aircraft

Answer: (C)

Substantial use is determined by the activity level of the airport's most capable aircraft that uses the field, measured by itinerant operations per year. The idea is to look at the largest aircraft category that visits the airport and see how often it operates there. If that largest aircraft accounts for 500 or more itinerant operations in a year, the airport is considered to have substantial use. This specific threshold—500 annual itinerant operations for the largest aircraft—is what the correct choice reflects.

Why this matters: it distinguishes airports based on meaningful activity from smaller, purely general aviation usage. The other options don’t fit the standard metric: setting a higher threshold (1,000) changes the cutoff; focusing on a small general aviation aircraft ignores the impact of the largest visiting aircraft; and saying any commercial service aircraft is sufficient lacks the defined activity threshold that determines substantial use.