Identify the physics principles contained within the following scenario. Explain how these principals connect to Einstein's theory of relativity or in modern applications in physics.

Mandy took a trip to Rome, Italy. She gazed out over the open ocean 20,000 feet below as her airplane began its descent to her final destination of Rome. It had been a long flight from New York to Rome, but she as she stretched, and her bones creaked as though she was old, she knew that in fact, she was a tiny bit younger than her compatriots back home, thanks to traveling at hundreds of miles per hour. In fact, time for her was running slowly compared to her friends in New York for two reasons: the speed at which she had traveled and the height of the airplane above the Earth. Neither, though, were noticeable.