A First Officer is a key member of an aircraft's flight crew, second in command to the Captain. Their primary responsibilities include assisting with flight operations, monitoring instruments, and communicating with air traffic control. The First Officer is trained to take over flying the aircraft if the Captain is unable to do so. In commercial aviation, First Officers typically hold a valid Airline Transport Pilot License (ATPL) and have significant flying experience. They undergo rigorous training and must demonstrate proficiency in various aircraft systems and emergency procedures. This role is essential for ensuring the safety and efficiency of flights.