private string Land(AerialVehicle a) { if (vehicles.Count < maxVehicles) { a.CurrentAltitude = 0; a.IsFlying = false; return($"{a} has landed."); } else { return($"{a} cannot land because the airport is full!"); } }
private string TakeOff(AerialVehicle a) { a.TakeOff(); return($"{a} has taken off."); }