July 2 (Reuters) - American Airlines ( AAL ) has agreed

to a provisional deal for 100 hydrogen-electric engines from

aviation startup ZeroAvia, the carrier said on Tuesday, to power

aircraft used in its regional routes.

The airline also increased its investment in the Hollister,

California-based company as part of its Series C financing

round, but did not disclose the details.

American first invested and signed a memorandum of

understanding with ZeroAvia, which is flight testing a prototype

for a 20-seat plane, in 2022.

The company is also designing an engine for larger aircraft

such as the Bombardier CRJ700, used by American on

some of its regional routes.

ZeroAvia's hydrogen-electric engines has the potential for

close to zero inflight emissions and use hydrogen in fuel cells

to power electric motors to turn an aircraft's propellers.

"Advancing the transition of commercial aviation to a

low-carbon future requires investments in promising

technologies, including alternate forms of propulsion," American

Airlines ( AAL ) CEO Robert Isom said in a statement.

The carrier has set a goal to achieve net-zero greenhouse

gas emissions by 2050.

Hydrogen is seen as a potential alternative for the aviation

industry, a major user of fossil fuels. It can be made from

fossil fuels or from water using electrolysis, although this is

an expensive process.