The conditional deal for Eve's four-seater air taxi, or electric vertical take-off and landing vehicle (eVTOL), includes an option for 200 more. United did not specify the conditions.

Delivery of Eve's first aircraft, which has a range of 60 miles, is expected as early as 2026, United said.

Electric air-taxi makers have pitched themselves as an alternative transportation for people in cities suffering from congested roads, but they are yet to receive clearance to fly passengers.

Nevertheless, they have attracted interest from airlines who are looking to boost their own green credentials.

United Airlines said it is investing in Eve in part due to the air-taxi maker's relationship with aircraft maker Embraer, which can provide access to parts and services.

The deal with Eve Air is United's second air taxi bet. The airline has also invested in Archer Aviation Inc, with whom it put down a deposit of $10 million last month for 100 eVTOLs.

(Reporting by Shivansh Tiwary in Bengaluru; Editing by Krishna Chandra Eluri)