Separate an aircraft departing behind a Category B or D departure on a parallel runway separated by 2,500 feet by ___ minute(s) if flight paths will cross.

• A. 1
• B. 3
• C. 4
• D. 2

Answer: (D)

When departures on parallel runways have crossing flight paths, you rely on time-based separation rather than relying on wide lateral spacing alone. With runways only 2,500 feet apart, the paths intersect in a way that a trailing aircraft could quickly enter the same airspace as the lead, so a minimum time gap is used to protect that crossing area. For Category B or D departures, the standard minimum behind a preceding departure is two minutes, which gives the lead aircraft enough time to clear the crossing point and allows wake effects to reduce before the follower reaches the same airspace. Shorter (one minute) would risk conflict, while longer (three or four minutes) is more conservative than required for this setup.