Aircraft On Ground (AOG) refers to a situation where an aircraft is unable to fly due to technical issues, maintenance, or other operational problems. This status can lead to significant delays and financial losses for airlines, as grounded planes cannot generate revenue. When an aircraft is classified as AOG, it often requires immediate attention to resolve the issue. Airlines typically prioritize these situations to minimize downtime, ensuring that necessary parts and maintenance crews are available to return the aircraft to service as quickly as possible.