To the right of each of your list's aircraft buttons are two lines of information.  The top line is the body type of the aircraft,, and the bottom line is the flight category of that aircraft (ARR = arrival, DEP = departure, and OVR = overflight).  Two special notices are also displayed in the bottom line, FF (free flight), and SPC (self spacing).

You can sort any of your aircraft lists by clicking the word "SORT," which brings up a list of possible sorting options:

None = no sorting rules
Entry Time = sort aircraft chronologically by the times they enter the simulation
Callsign = sort alphabetically by name
Type = sort by aircraft alphabetically by body type
Event Time = sort aircraft chronologically by the appearances of event prompts
Dist = sort aircraft spatially by distance from the airport
Category = sort aircraft alphabetically by flight category (ARR, DEP, OVR)
Free Flight = sort aircraft alphabetically by Free Flight status (FF or ATC)

You can also change the way aircraft are displayed in your aircraft lists by clicking the word "DSP" (display), which brings up a list of possible display formats:

Id/Status/Type only = your list will never expand to show the event prompts

Expand if event pending = your list will expand only when the event prompts exist

Always expand = your list will always be expanded regardless of event prompts (see left)

Event Prompts:

Event prompts serve to alert the aircraft's pilot, implying the need for action.  Observe the following event prompts:

        = The "HI" prompt indicates your aircraft has just appeared on your CTRL list.  You may need to check-in with the Air Traffic Controller on your new frequency.

    = The "FL?" prompt indicates your aircraft is approaching your VNAV TOD (Top of Descent).  You may need to request a lower flight level from your Air Traffic Controller

    = The "END" prompt indicates your aircraft is approaching the end of your FMS route.  You may need to land your plane or request approval to begin another leg of your flight (i.e., the UKW7 STAR)

    = The "MCP" prompt indicates your Free Flight aircraft is approaching your VNAV TOD.  You may need to set your MCP to a lower flight level to maintain your glide slope.

    = The "FF/ATC" prompt indicates your Free Flight aircraft is approaching the terminal area, or TRACON (Terminal Radar Approach Control)  where all aircraft are under Air Traffic Control.  You may need to request approval to cancel Free Flight and enter the terminal area from your Air Traffic Controller.