American Airlines announced it has entered into a conditional purchase agreement with clean aviation provider ZeroAvia for 100 hydrogen-electric engines intended to power regional jet aircraft with zero inflight emissions except for water vapor.

In addition, American has increased its investment in ZeroAvia, having made its first investment in the company in 2022; and has also now participated in the company’s Series C financing round. The engine agreement follows the Memorandum of Understanding the companies announced in 2022.

ZeroAvia is developing hydrogen-electric (fuel cell-powered) engines for commercial aircraft, which offer the potential for close to zero inflight emissions. The company is flight testing a prototype for a 20-seat plane and designing an engine for larger aircraft such as the Bombardier CRJ700, which American operates on certain regional routes.

Robert Isom, CEO of American, said advancing the transition of commercial aviation to a low-carbon future requires investments in promising technologies, including alternate forms of propulsion. This announcement, he said, “will help accelerate the development of technologies needed to power our industry and uphold our commitment to make American a sustainable airline so we can continue to deliver for customers for decades to come.”

ZeroAvia’s hydrogen-electric engines use hydrogen in fuel cells to generate electricity, which is then used to power electric motors to turn the aircraft’s propellers. The only inflight emission is low-temperature water vapor, and the lower intensity electrical systems have the potential to offer significant cost savings.