Second Day: No snowstorms, ice storms, freezing rain, tornadoes, hurricanes, or windstorms. In other words, no ugly weather to mess with flight patterns, or to delay departures or arrivals.
First Day: Healthy passengers. No cold or flu germs infecting other passengers or the crew. No need to divert for medical emergencies. No one needing emergency oxygen. No need to have paramedics meet the airplane. No falls, no bloody noses, no coughing. Healthy passengers mean a healthy working enviornment for us.