Which Airlines Have The Most Diverse Fleets? (2024)

Airline fleet diversity is a hotly debated topic. There are numerous examples of airlines that operate just a single aircraft model, such as Southwest or Ryanair with the Boeing 737 or easyJet with the Airbus A320 family. Even large international airlines like Emirates, which operates just Airbus A380s and Boeing 777s, seek to minimize maintenance and training costs by keeping to just a handful of models.

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However, there are also airlines that operate a wide variety of aircraft models and sub-types. Despite the conventional wisdom that fleet diversity leads to increased operation costs, these are some of the most profitable airlines on the planet. So why do some airlines choose fleet diversity, and which airlines have the most diverse fleets?

The airlines with the most diverse fleets

We looked at the ten airlines with the most diverse fleets and ranked them in the table below, based on the number of models followed by the number of sub-types. Data is quoted for individual airlines (not groups, such as IAG) and any wholly-owned subsidiaries and includes cargo aircraft where applicable.

We will examine the top three more closely below, but it is worth noting that the “big 3” Chinese carriers (Air China, China Southern, and China Eastern) are already high on the table for fleet diversity, and this is expected to increase further as they increasingly add Chinese-manufactured models and sub-types to their fleets.

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Another interesting note is that American Airlines, which has the world’s largest fleet, doesn’t make the top 10 in terms of diversity. This is because American Airlines has focused its fleet on just six models - four narrowbody (A319, A320, A321, and B737) and two widebody (B777 and B787) types.

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Delta Air Lines

Delta Air Lines has the most diverse global fleet, with 12 different models and 21 different sub-types in service. This is even after the retirement of its Boeing 777, MD-88, and MD-90 fleets during the COVID-19 pandemic. Its fleet diversity is boosted by its holding on to older aircraft—notably, the B757 and B767 fleets, which both have an average age of over 26 years—as well as its extensive regional fleets of CRJs and ERJs that it owns via its Delta Connection and Endeavor Air subsidiaries.

Photo: Delta Air Lines

Delta’s fleet diversity is set to increase further from next year, as it is set to start deliveries of the 100 Boeing 737 MAX 10s that it ordered in 2022. It will also add an additional sub-type in the form of the A350-1000, with 20 on order and deliveries set to begin in 2026.

Lufthansa

The German flag carrier has the world’s second-most diverse fleet, with 11 models and 16 sub-types in service. Its diversity is boosted by its enduring love for quad-jets. It is one of the few airlines to have the Airbus A340 in commercial service still (with both the -300 and -600 models), and it maintains a fleet of 27 Boeing 747s (eight -400s and 19 of the newer -8s) alongside its A380s.

Photo: Markus Mainka | Shutterstock.

Lufthansa’s fleet diversity will change considerably in the next few years. While it is adding new B787 and A350 aircraft (including a new sub-type in the A350-1000), it is doing so to replace its aging quad-jets. It will be retiring its B747-400s, A340-600s, and A340-300s in the medium term, and the net result will be that quad-jets will make up less than 15% of the fleet, down from more than 50% before the pandemic.

United Airlines

United Airlines has the third-most diverse fleet by number of models, but operates more sub-types than any other airline. This is because United has doubled down on its favored models. It owns all three sub-types of the Boeing 787, and six different sub-types across its fleet of over 500 Boeing 737s.

Photo: Lukas Souza | Simple Flying

United will add an additional sub-type in 2025 when it starts to take delivery of its order of Boeing 737 MAX 10s, meaning that it will also own all three variants of the MAX. However, its model diversity is set to reduce in the medium term, as deliveries from its massive order of 150 B787s in 2022 are set to replace its aging B767s.

Reasons why fleet diversity makes sense

While conventional wisdom is that fewer aircraft models mean lower operating expenses, there are multiple reasons why some airlines choose to maintain a very diverse fleet. These include:

• Mergers and acquisitions: Many larger airlines have acquired diverse fleets via mergers and acquisitions, and the acquired aircraft are retained as long as it makes financial sense / until newer aircraft replace them.
• Destinations: Larger airlines, especially those with hub-based models, serve a wide range of destinations, so fleet diversity is driven by the need to service anything from the longest intercontinental routes to short-feeder routes into hubs.
• Aircraft availability: Sometimes, it is as simple as the availability of the aircraft. If an airline cannot obtain production slots that meet its timeline, it might favor a competitive offering even if it doesn’t align with the current fleet.
• Negotiation power: While single-model airlines gain cost efficiencies, they are limited to discounts for volume purchases. Airlines with diverse fleets can play off the manufacturers against each other to obtain preferential pricing.
• Politics: Occasionally, macro factors such as pressure from governments or their agencies, other investments triggered by a purchase (e.g., in local suppliers), or quid-pro-quo deals will incentivize an airline to purchase a new aircraft model.

For most of these airlines with highly diverse fleets, the reasons for the diversity are numerous and often complex. What is clear is that each has found a way to overcome the increased operating expenses and exploit their diversity to drive significant operational growth.