Delta Air Lines Replaces Blended Winglets on Aircraft

Delta Air Lines is upgrading its narrowbody aircraft fleet by replacing older blended winglets with more advanced split scimitar winglets. This move aims to significantly improve fuel efficiency and reduce operational costs across its high-frequency domestic routes. The airline previously invested in blended winglets but is now adopting the newer technology to maximize performance.

Aviation's Drive for Efficiency and Sustainability

The aviation industry consistently seeks ways to become more efficient and environmentally friendly. Airlines face increasing pressure from rising fuel costs and stricter environmental regulations. This has led manufacturers to develop new engine technologies, lighter materials, and advanced aerodynamic features.

Winglets are a key innovation in this effort. These upward or split extensions at the wingtips reduce drag by disrupting wingtip vortices. This allows aircraft to fly the same distance using less fuel. Winglets are now common on new aircraft and are often retrofitted onto older planes.

Understanding Winglet Physics

Winglets work by managing airflow at the wingtips. As air moves over a wing, a pressure difference creates lift. At the wingtips, this pressure difference causes air to spiral upward and backward, forming vortices. These vortices generate induced drag, which reduces efficiency and increases fuel burn.

Winglets, with their vertical or split design, weaken these vortices. This allows the wing to produce the same amount of lift with less drag. The result is better fuel efficiency, longer flight ranges, and improved performance, especially on longer flights.

"Winglets disrupt this flow. Their vertical or split shape weakens the vortex and allows the wing to generate the same lift with less drag," according to industry experts.

Learjet was the first to use winglets on production aircraft in 1977. By the late 1980s, the technology appeared on commercial jets with the Boeing 747-400, which featured canted winglets. Companies like Aviation Partners later specialized in retrofitting winglets onto various Boeing aircraft.

Delta's Initial Investment in Blended Winglets

Wingtip modifications have evolved over time, reflecting advances in aerodynamics. Early designs included simple vertical endplates. A significant step forward was the development of canted winglets, angled outward and upward. These were seen on aircraft like the Boeing 747-400 and later on Airbus A330 and A340 models.

The next major improvement was the blended winglet. This design features a smooth, curved transition between the wing and the winglet. This smooth curve reduces interference drag and ensures better airflow. Blended winglets became widely adopted on Boeing 737, 757, and 767 aircraft.

Delta Air Lines was an early adopter of blended winglet technology. In 2007, the airline announced plans to install blended winglets on over 60 Boeing 737NG, 757-200, and 767-300ER aircraft. This commitment highlighted Delta's focus on fuel efficiency.

At the time, then-Chief Operating Officer Jim Whitehurst stated that these upgrades would lead to at least a 3.5% reduction in fuel burn and a minimum 5% increase in range. Delta eventually equipped most of its Boeing 737-800 and 737-900ER aircraft with blended winglets. Large portions of its 757-200, 757-300, and 767-300ER fleets also received this modification.

Even Delta's 737-700s featured blended winglets before the type was retired during the COVID-19 pandemic. This widespread adoption demonstrated Delta's long-term strategy to enhance its operational efficiency.

Transitioning to Split Scimitar Winglets

By the mid-2010s, Delta began exploring an even more advanced option: the split scimitar winglet. This design builds on the blended winglet by adding a downward-facing ventral fin beneath the wingtip. This dual-direction modification further reduces the wingtip vortex, leading to even greater drag reduction and improved fuel performance.

Split scimitar winglets became popular on Boeing 737 Next Generation (NG) aircraft, especially for airlines with frequent domestic flights, where even small efficiency gains quickly accumulate. Delta initiated this transition in 2014, placing an order for 70 firm and 30 optional split scimitar winglet systems for its 737-900ER fleet from Aviation Partners Boeing (APB).

APB is a joint venture between Boeing and Aviation Partners, responsible for developing these technologies. Four years later, Delta expanded its commitment with an order for another 60 systems for the same variant. More recently, in 2022, the airline announced plans to extend this retrofit program to its fleet of 737-800s. APB records show Delta ordered 77 shipsets for the 737-800 and an additional 29 for the 737-900ER in 2021.

According to ch-aviation data, Delta currently operates 77 Boeing 737-800s and 163 Boeing 737-900ERs. While blended winglets provided measurable benefits, the split scimitar design proved even more effective. Therefore, Delta is gradually replacing the older blended winglets with the newer split scimitar systems to maximize efficiency across its narrowbody fleet.

Blended vs. Split Scimitar: Performance Differences

The key difference lies in their design and performance. Blended winglets introduced a smooth, curved transition where the wing meets the winglet. This large radius curve helps maintain continuous airflow, reducing turbulence and concentrated vortices that cause drag. Aviation Partners notes that this design was over 60% more effective than earlier angular wingtip designs.

The split scimitar winglet enhances this foundation. It adds a downward-angled lower fin and reshapes the tip of the existing blended structure. This dual approach tackles the wingtip vortex from both above and below, further reducing drag. In practical terms, it improves the efficiency of the original blended winglet by approximately 2%.

While a 2% improvement might seem small for a single flight, the cumulative savings across hundreds of aircraft and thousands of flights annually are substantial. These gains translate into significant reductions in fuel costs and lower carbon emissions for Delta Air Lines.

The Next Generation: Boeing's AT Winglets on 737 MAX 10

Delta's investment in winglet technology directly translates into cost savings and aligns with its sustainability goals. The airline has an order for 100 Boeing 737 MAX 10 aircraft, the largest variant of the MAX family. While certification for the MAX 10 has faced delays, these aircraft will arrive with an updated winglet design.

The Boeing 737 MAX features what Boeing calls the Advanced Technology (AT) winglet. This split-tip design combines upward and downward extensions with a sharper angle at the tip, similar to the split scimitar but optimized for the MAX series. Boeing states that this configuration reduces fuel burn by about 2% by more efficiently redirecting wingtip vortices.

Additionally, the AT winglet incorporates Natural Laminar Flow (NLF) surfaces and specialized coatings. These features help maintain smooth airflow over the winglet surface, minimizing skin-friction drag and preventing turbulence. The split-up-and-down arrangement manages vortices more effectively than a single large blade, without requiring structural penalties associated with extending the wing span significantly.

For Delta, the AT winglets on its upcoming 737 MAX 10 fleet will represent the next phase of efficiency gains, building upon the split scimitar upgrades currently being installed on its 737 NG fleet.

Winglets Remain Key to Delta's Strategy

Winglets have evolved from experimental additions to a standard feature on modern commercial aircraft. Each new generation has incorporated lessons learned from previous designs, leading to incremental but meaningful improvements in performance and fuel efficiency. Today, the industry uses various designs, including blended winglets, split scimitars, raked tips, folding variants, and Airbus's sharklets.

These wingtip modifications allow airlines to achieve measurable performance boosts from existing airframes without major changes to the fuselage or engines. Delta has consistently followed this path. The airline initially adopted blended winglets for its narrowbody fleet to enhance efficiency and is now actively replacing them with the more effective split scimitar winglets.

This decision reflects Delta's commitment to securing even greater fuel savings and operational advantages, particularly across its high-frequency 737 operations. Looking ahead, this focus on efficiency will continue with the introduction of its new 737 MAX 10 fleet, equipped with Boeing's latest AT winglets. For Delta, winglets are a subtle yet critical technology, offering consistent improvements in fuel economy and supporting broader goals of cost management and environmental sustainability.