Delta is taking a different approach to futuristic aircraft like Boom's supersonic jet than its biggest competitors

• Delta Air Lines is the only major US carrier not to invest in Boom Supersonic's Overture jet or an eVTOL aircraft.
• CEO Ed Bastian told Fox Business that he has "a lot more questions than answers still," regarding Overture.

Large US carriers like American Airlines and United Airlines are placing bets on the aircraft of the future, like supersonic jets and electric vertical take-off and landing (eVTOL) aircraft, but one carrier has not made any investments just yet.

On Tuesday, American Airlines announced an order for 20 of Boom Supersonic's Overture aircraft, with an option for 40 more. The purchase puts the Texas-based carrier on track to become the largest operator of the ultra-fast plane.

United Airlines is the other US carrier to take interest in the Overture, having placed an order for 15, with an option for 35 more, in June 2021.

Meanwhile, both mainline carriers have also invested in electric aircraft, particularly eVTOLs.

American recently placed a pre-order for 250 of Vertical Aerospace's VX4 flying taxis, while United has deposited $10 million for 100 of Archer Aviation's "Midnight" eVTOLs. United has also invested in Heart Aerospace's ES-19 electric planes.

While American and United are inking agreements with startups promising a new future, Delta Air Lines is the only major US carrier not to invest in either. This may suggest Delta has a different vision for its future fleet, but Henry Harteveldt, travel analyst and president of Atmosphere Research Group, says that may not be the case.

Instead, he told Insider that he gives Delta "credit" for taking their time on making decisions.

"There's an opportunity cost for an airline when they're buying airplanes, and it doesn't matter what type of aircraft because there's only so much money that a carrier has available to invest," he said. "Airlines want to invest wisely to get the best possible return, so I don't see any problem with Delta choosing not to order the Overture or eVTOLs."

There is skepticism about Boom's Overture jet

According to Harteveldt, Delta may very well decide to buy a supersonic plane or an electric aircraft in the future, but they want to ensure the investment fits its business model and network.

"As far as Boom, there is a lot of skepticism within the aviation industry," he said. "Right now, it doesn't have an engine."

Delta CEO Ed Bastian confirmed his skepticism about the jet to Fox Business on Tuesday, saying he "has a lot more questions than answers still."

"Until we are confident that we could actually generate a reliable return from the aircraft, that's not where we're investing," he said.

Delta's Boeing 757-200s may have another 10 to 20 years in them

Harteveldt explained that while Delta does not have orders in for the Overture or eVTOLs, they are making decisions that will keep its current fleet flying longer.

Specifically, the carrier is retrofitting its Boeing 737-800, Boeing 737-900ER, and Boeing 757-200 aircraft with Split Scimitar Winglets made by Seattle-based Aviation Partners Boeing to reduce carbon emissions.

Harteveldt says the inclusion of the 757 is particularly surprising.

"The 757 is an excellent airplane, but it is no longer in production, and there is a lot of curiosity of the future of the aircraft," he said. "But, clearly, the plane is serving an important role for Delta and they have found a way to keep them flying for another 10 to 20 years."

"They may not be the greenest planes, as the engines are not as fuel-efficient as some of the newer generation ones, but Delta is keeping dozens of 757s out of the landfill," Harteveldt continued.

Delta shouldn't buy certain planes just because its competitors are

It is still possible we will see a Delta order for an eVTOL or Overture in the future, Harteveldt said, saying if Delta sees either fit its business strategy, it will order it. But, he emphasized the carrier "shouldn't feel compelled to order the plane just because other airlines are doing so."

What matters for Delta is that it finds the aircraft that makes sense for it from a business standpoint, from a route and network standpoint, and if it makes money for the company and attracts more customers." he said. "The race is just starting."