What is the purpose of airplane tail numbers?

Answer 1

Every aircraft is built to specific regulations and must be certified by the FAA. Each aircraft is then identified by a Regisration Number or the Tail Number. The aircraft will have an official document, usually mounted on a wall in the cockpit or just outside of it, that identifies the aircraft as having been certified for a specific type. This will identify the aircraft type which provides information as to the gross weight that it will operate. The tail number must be displayed so an observer can identify the aircraft. This helps people report an aircraft that is violating flight rules or help identify it for other reasons. Most operators of large passenger airlines, paints a portion of the Tail Number (usually 3 numberals or alpha characters) on the Nose Landing Gear doors. This allows the ground crew to easily see the tail number. The first Letter of the Tail Number identifies the country of origin where the aircraft is registered. "N" is used for all aicraft in the USA. "G" is used for aircraft registered in Canada.