What percentage is used as a minimum for N1 in flight?

The minimum percentage used for N1 in flight is 67%. This percentage is critical because it represents the optimum operational limits of the engine during various phases of flight. Maintaining N1 above this threshold ensures that the engine is producing sufficient thrust while managing efficiency and safety standards.

Lower values such as 60%, 61%, or 70% do not meet the required threshold as specified for optimal engine performance during crucial flight operations. Operating at or above 67% N1 helps ensure that the engines can offer the necessary performance while also adhering to safety protocols, especially during takeoff and climb phases where thrust demands are high.