The instructor is a specified role within AeroPlus. Instructors can update the progress reports of student pilots and they can specify their own timeschedule so that studentpilots can reserve flying lessons together with an instructor and match the availability of an aircraft with that of an instructor. If a pilot is not checked out on a specific aircraft and as thus not linked to that aircraft, then that pilot can still make a reservation on that aircraft, but only when booked together with an instructor. So, in that case the availability of an instructor needs to be available from within AeroPlus.
The only way a studentpilot can know if an instructor is available in combination with an aircraft is for an instructor to specify his availability. Often, instructors work only parttime at a specific flyingschool and only teach the art of flying on specific aircraft. The availability can be specified in the above form. If an instructor teaches every Wednesday and Friday from January until June, you can specify this as a recurring (1) availability. As an instructor, you can print your daily workschedule (2) giving you information on which students you will be flying with that day. Studentpilots can make reservations themselves through the internet or using the iPhone/iPad apps or you can have a frontdesk employee of the flightschool or aeroclub to make the reservations for them. In that case, the frontdesk employee needs to be logged in with the role of "administrator".