Aircraft on ground

Aircraft On Ground or AOG is a term in aviation maintenance indicating that a problem is serious enough to prevent an aircraft from flying.^[1] This can involve problems as simple as a light bulb being out, or as complex as a damaged engine. Boeing estimates that a 1-2 hour AOG situation will cost an airline from $10,000 to $20,000 and possibly even as high as $150,000 per hour depending on the type of aircraft and route flown.^[2]

A group of Airbus aircraft being sealed for long-term grounding at Noi Bai International Airport. Most of them are grounded due to technical issues and are not planned to be withdrawn permanently from the airline's nominal fleet.

Causes of AOG incidents

AOG incidents can arise from various factors, including:^{[citation needed]}

• Mechanical failures: Unexpected mechanical issues or failures during flight or pre-flight checks can ground an aircraft.
• Maintenance delays: Scheduled maintenance that extends beyond the expected timeframe can result in AOG status.
• Supply chain issues: Delays in obtaining necessary parts or components can hinder timely repairs, leading to extended grounding periods^[3]
• Regulatory compliance: Aircraft may be grounded due to non-compliance with safety regulations or certification requirements.
• AOG can also refer to an aircraft waiting for a flight crew at a different airport, where flight crew are not available. Crew scheduling can designate an inbound deadheading crew, to operate this flight, as "AOG" which makes this crew the highest priority to get seats on the flight. Passengers, even in first class can be "bumped" to accommodate the AOG crew. ^[4]