Final answer:
After being stored for a long time, the frequency of an aircraft's engines will be lower pitched but will increase in pitch as the plane slows down.
Step-by-step explanation:
After an aircraft has been stored for an extended period of time, the frequency of the plane's engines will be lower pitched according to the baggage handler but will increase in pitch as the plane slows to a stop. This is because when the engines are not in use for a long time, they may experience some wear and tear, causing a change in their frequency. However, as the plane slows down and the engine's RPM (revolutions per minute) decreases, the frequency of the engine will increase, resulting in a higher pitch sound.