Takeoff involves operating engines at maximum thrust. This induces high-frequency vibrations. If the takeoff thrust setting causes the engine or airframe to vibrate at a frequency matching the natural harmonic of a specific component (e.g., a turbine blade or wing spar), mechanical resonance occurs. This resonance amplifies stress at the molecular boundaries of the metal, causing a dormant crack to become "active" and propagate at speeds far exceeding standard fatigue rates.