On Dec. 23, a friend shared news of a Christmas miracle, of sorts. She had just cancelled nonrefundable Delta airline tickets from Minneapolis to New York City because her daughter had a sudden, raging fever. The person at Delta who accepted the cancellation waived the usual $150-per-ticket change fee, saving her family of three $450. Delta’s contract of carriage is silent on the issue of sick passengers who want to delay a flight, so perhaps my friend benefited from a random act of holiday cheer. A cynic might say that during this busy flying season, Delta could easily fill those seats and probably had oversold the flight in the first place. But to my friend, the gesture felt like the best kind of present: unexpected and wonderful.