This is an old revision of the document!
Aircraft on ground or AOG is a term in aviation maintenance indicating that a problem is serious enough to prevent an aircraft from flying.
There is a possibility to mark a checkbox AOG (Aircraft On Ground) in the section Maintenance > Scheduled Maintenance > Edit Scheduled Maintenance
The appearance changes in the Planned Flights section from red square to pink with the indication AOG and the airport where the aircraft has been grounded.