Delta does things differently than most airlines, and that includes the way it buys airplanes.

While most big carriers replenish and expand their fleets with brand new jets, which are either leased or purchased, Delta has purchased a mix of new and used aircraft over the past several years.

Ed Lohr, Delta’s Managing Director of Fleet Strategy, explained that the airline looks at the entire cost of jet – the purchase price, the maintenance costs, fuel efficiency and other factors – before making decisions. Often, used aircraft make the most economic sense for the airline.

And thanks to Delta’s TechOps aviation maintenance team, used planes can be maintained and retrofitted with entirely new interiors, providing a superior customer experience even though the jet may be a few years old.

And Delta typically purchases planes outright rather than leasing them.

“We do have a different strategy than most of our competitors,” Lohr said. “When you have a strong balance sheet like we do, a great TechOps organization like we do, it gives you a lot more flexibility to take advantage of opportunities when they come up.”

For example, Delta acquired 88 used Boeing 717 after Southwest inherited them in its merger with AirTran Airways. Those jets fill a critical role in Delta’s domestic network, and were given nose-to-tail revamps before entering service.

Delta has similarly scoured the world for used MD-90 jets, reliable narrowbodies that are also dramatically upgraded and brought into the fleet at a very reasonable price.

Still, Delta will buy new when it makes sense. For example, the airline recently ordered 25 fuel-efficient Airbus A350-900s to fly primarily long-haul trans-Pacific routes starting in 2017.

The aircraft strategy is one of the reasons Delta has been able to pay off more than $10 billion in debt since 2008, and has seen its credit rating rise to just one notch below investment grade. Less money is tied up in expensive new jets, and instead can be invested in airport facilities, operational performance, new technology and on-board improvements to enhance the customer experience.

“The days of buying just one brand of aircraft, or signing huge orders all at once, those are definitely over,” Lohr said. “At least, they are for us.”

- Trebor Banstetter