Caterpillar, BNSF Railway, Chevron pursue hydrogen-powered locomotive

• United Airlines on Monday secured the right to buy up to 100 hydrogen engines for its aircraft.

Why it matters: Transportation represents the largest share of U.S. greenhouse gas emissions, which contribute to climate change.

Yes, but: Producing hydrogen isn't always environmentally friendly, as fossil fuels are often used to make it.

Details: Caterpillar’s Progress Rail will develop a hydrogen rail system, Chevron will deliver the fueling setup, and BNSF will demonstrate the technology once it's ready.

• United invested in ZeroAvia's hydrogen-electric jet engine, which the airline said, “could be retrofit to existing United Express aircraft as early as 2028.”