The Area of Operations (AO), or 'ops box', is where you conduct your reconnaissance activities each patrol. In Recon this is the 5000x5000 pixel square where you land and do your patrol. During the patrol, no friendly activities will take place in this specific area, including aircraft and other operations unless cleared through the patrol leader (you), to minimize the occurrence of blue on blue incidents (friendly fire). Whenever an ETA is given for an aircraft or other object moving into the AO, this is the time until said object reaches the boundary of the AO. Thus, the ETA on an extraction is not the time that the chopper will land at the LZ, but the time that the chopper first enters the boundaries of your AO.
There is a chance for a memo stating that your ops box has been lost for 7 days, any operation within the 7 days will have the chance of friendly support firing into the AO without the commanders authorization.
In real life, LRRP's usually would operate in a 4km by 4km operation box, and this is the basis for the AO in Recon.