public class FlyCommand
  implements CommandExecutor
{
  public StartCommand(Main plugin)
  {
    plugin.getCommand("fly").setExecutor(this);
  }

  public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args)
  {
    if (!(sender instanceof Player))
    {
      sender.sendMessage("Eingabe in der Konsole nicht möglich");
      return true;
    }
    Player player = (Player) sender;

    toggleFly(player)
    return true;
  }

public void toggleFly(Player player){
    //Alte Fly Methode hier rein
  }
}