It's a known issue. In summary
1) Commands didn't work initially so they are being reworked from scratch by a programmer who's also working on another aspect of the sim (can't remember which one to be honest), so it takes some time.
2) In order to avoid confusion between working and non-working commands, all the non-working commands have been temporarily removed from the radio menu and only the working commands remain.
3) Any airfield with an airfield AI object placed in the FMB has ground control functions. These functions are used to place a "T" shaped marker on the start of the active runway (it changes depending on wind, as planes should land and take-off into the wind) and issue landing clearance to aircraft. The way it works is you overfly the field and the ground controller will tell the flight to join the landing circuit. Once the command is issued (individually to each aircraft) the AI wingmen will break away from the formation and set up their approach.
In short, until the rest of the radio commands are redone, just overfly the airfield once to have your wingmen break away and set up their own landings. You don't have to wait for them to land after that and there's no penalty if you don't follow the exact sequence the ground controller gives.
Overfly->Listen for tower commands->Land
Hope it helps as a temporary workaround.
