It reflects sunlight.
This is crucial as when sunlight is absorbed by an aircraft, this heats up the body of an airplane. Painting a passenger plane white minimises both the heating and potential damage from solar radiation not only when the airplane is in flight, but also when it's parked on the runway.
The biggest reason for flying at higher altitudes lies in fuel efficiency. The thin air creates less drag on the aircraft, which means the plane can use less fuel in order to maintain speed. Less wind resistance, more power, less effort, so to speak.
MORE DETAILS
While fuel dumps don't happen every day, they're also not uncommon. Nor do they usually represent a major emergency. In fact if an aircraft is taking the time to dump fuel before landing, that's likely an indication that the issue forcing the plane to land is serious but not critical.
MORE DETAILS
The spraying of airplanes as they land is a tradition known as the “water salute.” As explained by Wikipedia, it's performed for ceremonial purposes, such as the retirement of an airplane. When an airplane makes its final flight, it's honored with the water salute once it lands on the tarmac.
MORE DETAILS
Whether flying at night or during the day, pilots need to see some kind of horizon. They use this to determine the airplane's attitude. At night pilots will turn their gaze from outside to inside and use the artificial horizon. The artificial horizon is normally a simply globe split into two hemispheres.
MORE DETAILS
The simple answer is yes, pilots do, and are allowed to sleep during flight but there are strict rules controlling this practice. Pilots would only normally sleep on long haul flights, although sleep on short haul flights is permitted to avoid the effects of fatigue.
MORE DETAILS