Want a climate-friendly flight? It's going to take a while and cost you more

“It's a lot easier to pack a heavy battery into a vehicle if you don't have to lift it off the ground,” said Gernot Wagner, a climate economist at Columbia University.

That means sustainable aviation fuel has become the industry's best hope to achieve its promise of net zero emissions by 2050. Aviation produces 2% to 3% of worldwide carbon emissions, but its share is expected to grow as travel increases and other industries become greener.

Sustainable fuel, however, accounts for just 0.1% of all jet fuel. Made from sources like used cooking oil and plant waste, SAF can be blended with conventional jet fuel but costs much more.

Suppliers are “going to be able to kind of set the price," Molly Wilkinson, an American Airlines vice president, said at the air show. "And we fear that at that point, that price eventually is going to trickle down to the passenger in some form of a ticket price.”