Southwest Airlines is by far the world’s largest operator of the Boeing 737, currently operating a staggering 810 examples of the aircraft across three different variants – the 737-700, 737-800, and 737 MAX 8. In fact, the 737 is the only aircraft type operated by the low-cost carrier. However, the carrier is now reducing the number of 737 NGs (737-700s and 737-800s) in its fleet, with the goal of retiring them completely by 2031.
In this article, we will take a closer look at why Southwest Airlines may be looking to reduce the number of Boeing 737 NGs in its fleet. We will also examine the role of the Boeing 737 in Southwest Airlines’ fleet and its impact on the wider aviation industry.
Higher Operating Costs
Since the Boeing 737 NG was first delivered to Southwest Airlines, newer aircraft have been developed that are much more fuel-efficient and have lower operating costs, namely the Boeing 737 MAX series. Each 737 MAX is powered by two CFM LEAP-1B engines, which are larger and more advanced than those on previous models. Combined with aerodynamic improvements such as advanced winglets and lighter materials, the MAX offers around 14-20% greater fuel efficiency compared to the previous 737 NG models.
Improving fuel use translates directly into lower fuel cost per seat, which is one of the biggest costs for airlines, so it is easy to see why the carrier is keen to focus on modernizing its fleet. Greater fuel efficiency will also support Southwest Airlines in reaching its own ambitious sustainability targets, as well as those of the wider aviation industry.
Replacing older Boeing 737 NGs helps reduce not only fuel costs, but also maintenance costs, and likely downtime/repairs, since older aircraft tend to require more maintenance, which we will look into in more detail below.
Aging Aircraft
Southwest Airlines’ Boeing 737 NG fleet is much older than its younger 737 MAX aircraft, with an average age of around 19 years old ( 737-700) and 11 years old ( 737-800), according to the latest data from ch-aviation. As a result, Southwest Airlines aims to retire up to 55 Boeing 737 NGs each year, with a view to the final aircraft leaving its fleet in 2031.
Southwest’s 737‑700s and ‑800s have been in service for many years, so they are more likely to require increasingly frequent and costly maintenance, and show increased potential for structural fatigue issues. For example, the carrier has recently had to inspect its 737 NGs for issues like cracks in the fuselage, as mandated by the Federal Aviation Administration (FAA).
Growing Demand For Narrowbody Aircraft
Demand for narrowbody aircraft is only set to grow over the coming years, compounded by the problems with Pratt & Whitney’s GTF engines, which have led to some airlines looking to temporarily fill shortfalls in their fleets. With increased demand for second-hand aircraft, Southwest is likely to be able to achieve a higher price for each of its Boeing 737 NGs, making the sale of its older aircraft a more viable option than it was previously.
As reported by FlightGlobal, in September 2024, Southwest Airlines’ CEO, Bob Jordan, spoke about the strategic overhaul taking place at the carrier and how it can capitalize on this growing demand for second-hand aircraft.
“We have a unique opportunity to capture value and earnings on excess aircraft we do not need with our moderate growth plan. With that in mind, we are pursuing direct sales of [737]-800 aircraft. We are also looking at sale-leaseback where we can be opportunistic.”
Southwest & The Boeing 737
Southwest Airlines took delivery of its first Boeing 737 (a 737-200) in 1971, launching flights from Dallas Love Field (DAL) to both Houston William P. Hobby Airport (HOU) and San Antonio International Airport (SAT). The latest data from ch-aviation shows that today, the carrier operates a total of 810 Boeing 737s, making it by far the world’s largest operator of the aircraft. This is spread across three different variants, which are listed in the table below, together with their passenger capacities:
Southwest also has an outstanding order for a further 196 Boeing 737 MAX 8s on order, as well as 314 737 MAX 7s, which will be a new aircraft type for the carrier when it joins the fleet (deliveries are currently planned to commence in 2026). The low-cost carrier’s CEO, Bob Jordan, went on to confirm its commitment to Boeing and the 737.
“We have a long history with Boeing, dating back more than 50 years to the day we commenced service with three Boeing 737 aircraft serving three cities. They’re part of our history and part of our future as we continue to recognize the many efficiencies and cost savings of a single fleet.”
Aiming For An All-Boeing 737 MAX Fleet
As Southwest’s 737 NGs are retired, they will be replaced by the carrier’s incoming 737 MAX 7 and 737 MAX 8 aircraft. Such fleet simplification will allow the carrier to further reduce the complexity that comes with operating several different aircraft types. In fact, with 273 737 MAX 8s, the airline’s 737 MAX fleet is now larger than its fleet of 203 737-800s.
The 737 MAX is the latest generation of Boeing’s popular 737 narrowbody aircraft series. It was designed to improve fuel efficiency, reduce operating costs, and compete directly with the Airbus A320neo family. The aircraft entered commercial service in May 2017 with Malindo Air, operating a flight between Kuala Lumpur International Airport (KUL) and Singapore Changi Airport (SIN).
Two variants of the 737 MAX are currently available: the MAX 8 and MAX 9. The smaller MAX 7 and larger MAX 10 are set to receive their certification and enter commercial service before the end of 2026. However, this date has already been pushed back by several years from the original estimates of 2023-2024. Southwest will be the launch customer for the MAX 7 when it is eventually delivered, while United Airlines will be the world’s first carrier to take delivery of the MAX 10.
The Setbacks Faced By The Boeing 737 MAX
However, the 737 MAX program has not been without its problems. Two fatal crashes in the aircraft’s early years led to the grounding of all MAX aircraft worldwide. The first occurred in October 2018, when a Lion Air 737 MAX 8 operating Flight 610 from Jakarta Soekarno-Hatta International Airport (CGK) to Depati Amir Airport (PGK) crashed into the Java Sea, killing all 189 passengers and crew members onboard.
Then, in March 2019, Ethiopian Airlines Flight 302 crashed on take-off from Addis Ababa Bole International Airport (ADD), bound for Nairobi Jomo Kenyatta International Airport (NBO). All 157 passengers and crew members onboard were killed, and the aircraft was grounded shortly after.
The global grounding of the 737 lasted nearly two years, making it one of the most extensive in aviation history. In addition to financial losses, Boeing was dealt a significant blow to its reputation, which was exacerbated when an Alaska Airlines 737 MAX 9 suffered a door blowout in January 2024. Luckily, nobody was seriously hurt in the incident, but its impact was felt across the wider aviation industry. Deliveries have since resumed, but the US manufacturer has been left with a sizable backlog to clear, with airlines around the world crying out for more short-haul narrowbody aircraft.
About Southwest Airlines
Southwest was founded in 1967 by Herb Kelleher and Rollin King as Air Southwest, and later became Southwest Airlines in 1971. That same year, the carrier started flying between Dallas Love Field (DAL), Houston William P. Hobby Airport (HOU), and San Antonio International Airport (SAT) – the so‑called “Texas Triangle.” Because it initially operated intrastate, the airline could avoid certain federal regulations, enabling it to keep costs low.
The US Airline Deregulation Act of 1978 allowed Southwest to expand its reach further across the country, operating point-to-point routes with frequent services, quick turnaround, and low fares. This was a stark contrast to the traditional hub-and-spoke business model seen previously by the major US legacy carriers, and laid the foundations for the concept of the low-cost carrier, which has gone on to be emulated around the world.
Southwest continued to grow and was able to turn a profit every year of its operation until the COVID-19 pandemic struck in 2020. However, the carrier has since recovered and continues to go from strength to strength, including significant expansion into the Hawaii market, taking customers away from Hawaiian Airlines.