With only weeks to go until the aviation community meets in Atlanta for MRO Americas 2025, this week's #FlightFriday looks at a carrier causing a stir: Southwest Airlines.

Southwest relies exclusively on the Boeing 737s for its operations. More specifically, it relies on only three types of the 737. The current in-service fleet consists of almost 350 737-700s, with an average age of 19 years, just over 200 737-800s, with an average fleet age just shy of 10 years, and more than 250 737-8s, with an average age still under 3.5 years.

Following the MAX grounding in March 2019, Southwest went into the pandemic only operating -700s and -800s. It had a larger 737-700 fleet of 500 aircraft fitted in a 143-seat layout,  compared to a little over 200 of the 175-seat 737-800s. Back then, the -700 accounted for more than three-quarters of Southwest's monthly flights.

As no new MAX aircraft could be delivered to Southwest due to the grounding, the -700s and -800s remained in service. Since deliveries resumed in February 2021, more than 200 175-seat MAX aircraft have been delivered to the airline. That has allowed Southwest to remove some of its -700s from service, which has seen that sub-fleet contract to some 350 aircraft. 

The MAXs have the same 175-seat layout as the -800s. The pivot of switching out a 143-seat aircraft with a 175-seat aircraft bolsters Southwest’s available seat miles (ASM) and also helps the airline become greener, because the MAX is much more efficient than a -700 and has more seats, therefore lowering the emissions per ASM figure.

The increase in the MAX fleet means that as a proportion of aircraft flying, the MAX now equates to a little under 30% of all Southwest flights, with the -700 now accounting for less than half. 

The airline has more than 200 737-8s on order, alongside 300 orders for the still yet-to-be-certified 737-7. Southwest has almost enough aircraft on order to replace its legacy 737NG fleet one-for-one with MAX aircraft.

This data was put together using Aviation Week’s Tracked Aircraft Utilization database Find out more