/* Ensure airport class is valid (changing NewGRFs). */

		_selected_airport_class = Clamp(_selected_airport_class, APC_BEGIN, (AirportClassID)(AirportClass::GetClassCount() - 1));

		const AirportClass *ac = AirportClass::Get(_selected_airport_class);

		this->vscroll->SetCount(ac->GetSpecCount());

		/* Ensure the airport index is valid for this class (changing NewGRFs). */

		_selected_airport_index = Clamp(_selected_airport_index, -1, ac->GetSpecCount() - 1);

		/* Only when no valid airport was selected, we want to select the first airport. */

		bool selectFirstAirport = true;

		if (_selected_airport_index != -1) {

			const AirportSpec *as = ac->GetSpec(_selected_airport_index);

			if (as->IsAvailable()) {

				/* Ensure the airport layout is valid. */

				_selected_airport_layout = Clamp(_selected_airport_layout, 0, as->num_table - 1);

				selectFirstAirport = false;

				this->UpdateSelectSize();

			}

		}

		if (selectFirstAirport) this->SelectFirstAvailableAirport(true);