Which altitude band is common on eastern mountainous routes?

Which altitude band is common on eastern mountainous routes?

• A. FL100 and above
• B. FL200 and above
• C. FL300 and above
• D. FL400 and above

Answer: (C)

In mountainous terrain, airways are designed to keep traffic well above the highest obstacles, so routes through high-elevation areas become part of the upper airspace. That means flying at higher flight levels to ensure adequate terrain clearance and orderly separation from other aircraft. Eastern mountainous routes are typically designated for upper airspace, where aircraft cruise at around and above flight level 300. This provides a comfortable buffer above the terrain of the eastern mountains and aligns with standard ATC separation practices for higher-altitude traffic. Lower altitude bands would risk insufficient clearance over tall peaks, while even higher bands (like FL400 and above) are less commonly needed as the regular traffic mix in these routes already sits in the FL300+ range. Thus, FL300 and above is the common altitude band for these eastern mountainous routes.

In mountainous terrain, airways are designed to keep traffic well above the highest obstacles, so routes through high-elevation areas become part of the upper airspace. That means flying at higher flight levels to ensure adequate terrain clearance and orderly separation from other aircraft. Eastern mountainous routes are typically designated for upper airspace, where aircraft cruise at around and above flight level 300. This provides a comfortable buffer above the terrain of the eastern mountains and aligns with standard ATC separation practices for higher-altitude traffic.

Lower altitude bands would risk insufficient clearance over tall peaks, while even higher bands (like FL400 and above) are less commonly needed as the regular traffic mix in these routes already sits in the FL300+ range. Thus, FL300 and above is the common altitude band for these eastern mountainous routes.