Southwest Airlines has become one of the world’s largest airlines and budget carriers. Over the years, a loyal following emerged thanks to the fact that, even for its most basic fares, Southwest Airlines offered passengers two free checked bags, no change or cancel fees, and a non-expiring flight credit. However, the airline has recently made some major changes to its pricing structure, including discontinuing free checked bags and introducing a requirement to pay for seating options.

Beyond its unique value proposition, the carrier is famous for exclusively operating the Boeing 737. As the airline navigates uncertain times, it has reinvested in the aircraft family with extensive investment in and deployment of the 737 MAX. But why is Southwest so eager to discard its older 737NGs?

A Look At Southwest Airlines’ Past Fleet

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Southwest was incorporated as Air Southwest Co. in Texas in 1967. However, due to prolonged legal challenges over its validity from incumbent carriers, it did not operate its first revenue flight until June 18, 1971. Though its first flight was operated by a 737-200, a first-generation Boeing 737, the original plan did not include utilizing Boeing’s most popular aircraft. Originally, Southwest wanted to bring lower fares to the Texas market, which meant finding ways to keep costs low.

As such, co-founder Rollin King wanted to purchase a used Lockheed L-188 turboprop aircraft from American Airlines, which had a low acquisition cost. However, due to the 1970s recession, airlines across the industry faced declining profits, and some canceled aircraft orders previously made. Luckily for Southwest, Aloha, Pacific Southwest, and Air California canceled some of their orders for the 737, forcing the manufacturer to put them up for sale at a discounted price.

Suddenly, Southwest had a fleet of three brand-new jets. Since then, Southwest Airlines has become a loyal Boeing 737 customer. Throughout its existence, it has operated six 737 models and was the launch customer for three of them. Aside from a few brief periods in the 1980s when the carrier leased 727s, Southwest has stuck to its single-fleet strategy. Moving forward, it looks to remain loyal to the aircraft family with its heavy investment in the latest iteration of the aircraft, the 737 MAX.

A Longstanding Relationship: Southwest Airlines & The Boeing 737NG

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As previously mentioned, Southwest Airlines has operated several different Boeing 737 variants, but the airline currently mainly relies heavily on the 737NG series. This popular series of narrowbody aircraft preceded the recent Boeing 737 MAX series, and the airline’s 737-700 and -800 models continue to play a vital role in daily operations. According to ch-aviation, its most popular model is the 737-700. The carrier operates 310 in total, of which 24 are currently parked.

The Boeing 737NG series debuted in 1997. Since then, over 7,000 different aircraft have been delivered. It featured a redesigned wing that utilizes a larger area and wider wingspan. Additionally, the family has greater fuel capacity, a higher maximum takeoff weight, and longer range than the Boeing 737 Classic series. The table below details the 737NG’s performance specifications, per Boeing.

Specifically, Southwest Airlines was the launch customer for the program, as it took delivery of the first aircraft in December 1997. It originally placed an order for 63 Boeing 737-700s, and, by June 2018, Southwest Airlines was operating over 500 Boeing 737NG series jets.

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The Economics Of Aging Aircraft

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According to ch-aviation, the airline’s fleet of Boeing 737-700s has an average age of 19.8 years, and its fleet of Boeing 737-800s has an average age of 10.5 years. These aircraft are aging, resulting in a significant increase in their economic burden over the years. The older aircraft in the airline’s fleet are now over 20 years old, meaning the airline will likely look to replace them in the coming years.

As aircraft age, they require more frequent and intensive inspections, part replacements, and overhauls. For example, older 737-700s are subject to heavy checks that can take weeks and cost millions per plane. Additionally, older Boeing 737 NG aircraft are considerably less efficient than newer narrowbody aircraft.

Newer aircraft like the Boeing 737 MAX offer double-digit gains in fuel burn reduction compared to the older NG series. Older 737NG aircraft also lack modern amenities like power outlets, upgraded interiors, and quieter cabins. As a result, Southwest Airlines is looking to gradually phase out its fleet of 737NG aircraft in favor of the newer and more efficient 737 MAX series.

Fleet Simplification & MAX Migration

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As previously mentioned, Southwest Airlines is looking to begin phasing out its fleet of Boeing 737NG aircraft. Instead, the airline will replace the aircraft with the 737 MAX series, which are considerably more efficient and newer. According to ch-aviation, Southwest Airlines has already taken delivery of 303 Boeing 737 MAX 8 aircraft. Additionally, the airline has 193 yet to be delivered, as well as 259 examples of the as-yet-uncertified MAX 7.

The Boeing 737 MAX series offers several strategic advantages beyond just better fuel economy. Standardizing around one newer model means reduced pilot training variability, simpler maintenance processes, and leaner spare parts inventories. Overall, Southwest Airlines will rely on these factors to provide lower operating costs and fewer logistical issues.

Because of this, Southwest Airlines will look to simplify its fleet. For example, the 737 MAX 7 will directly replace the 737-700 fleet, as it will offer more seats and better fuel efficiency. This will help the airline maintain its existing route structure while improving its cost-per-seat margins. For an airline like Southwest that depends on high aircraft utilization and tight scheduling, the transition to the 737 MAX family makes strategic sense.

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A Closer Look At Southwest Airlines’ Current Fleet

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Southwest Airlines is notable for the fact that it only flies Boeing 737 series aircraft. Since it was founded as Air Southwest nearly 60 years ago, the airline has grown into the largest low-cost carrier in the world. It remains the fourth-largest airline in the US, trailing only American Airlines, Delta Air Lines, and United Airlines.

Historically, Southwest Airlines operated several different older 737 variants, including the Boeing 737-200, 737-300, and 737-500. However, the airline has since retired all of these aircraft, alongside 88 Boeing 717-200s that were acquired after it acquired AirTran Airways, although Southwest never operated these aircraft. Instead, it leased them to Delta Air Lines rather than integrating them into its fleet.

Currently, Southwest Airlines flies over 300 737-700s, which have an average age of 19.8 years, and the oldest aircraft in its 737-700 fleet is N7824A, which is almost 25 years old. It also operates a fleet of 737-800 aircraft with an average age of 10.5 years, and the oldest aircraft in its 737-800 fleet is N8301J, with an age of 14.01 years. Its 737 MAX 8 fleet is obviously much younger, as it has an average age of just 3.5 years.

The Benefits Of The Boeing 737 MAX

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As previously mentioned, the 737 MAX series is a direct improvement to the Boeing 737NG series, and it has been in production since 2014. The first 737 MAX aircraft was delivered to Malindo Air in May 2017, and, since then, nearly 2,000 737 MAX variants have been produced.

Currently, only the 737 MAX 8 and MAX 9 are certified, as Boeing is still awaiting certification for the MAX 7 and MAX 10. The 737 MAX series includes the more efficient CFM International LEAP engines, which each provide the aircraft with nearly 30,000 pounds of thrust. This powerful engine helps the aircraft achieve the performance specifications detailed in the table below.

The 737 MAX family also includes several other upgrades, including split-tip winglets. These unique winglets are designed to reduce vortex drag and further improve fuel efficiency. Other small aerodynamic improvements include a recontoured tailcone, revised APU exhaust, and an aft body vortex generator removal.