According to a recent regulatory filing, Southwest Airlines has increased its Boeing 737 MAX 7 order by 34 aircraft, bringing the total order book for that airplane to 234 units.

The airline said it would exercise options to increase its Boeing 737 MAX 7 order by 34 planes. Before making a move, Southwest had 350 firm orders, including 150 Boeing 737 MAX 8 and 200 Boeing 737 MAX 7. Next year, it expects to accept part of the total 34 deliveries of the smallest variant.

The deliveries of new Boeing 737 MAXs mean the retirement of the carrier’s‎ older aircraft. Over the next 10- 15 years, Southwest will be retiring 30-35 Boeing 737-700 jets yearly.

United Airlines and Alaska Airlines have also upped their Boeing 737 MAX orders in recent months.