Joby Aviation Inc., the electric aircraft company working on flying taxis, has increased the size of its contract with the U.S. Defense Department to as much as $75 million. The company announced the new agreement on Wednesday.

The California-based company makes electric-powered, vertical takeoff and landing vehicles, or eVTOLs. Its Defense Department deal, which runs through 2025, more than doubled in size from a $30 million value and now includes the U.S. Marine Corps. The contract reflects recent interest from Washington in electric aircraft that are cheaper to maintain than traditional helicopters and have zero emissions.

"Continued momentum with government customers has always been an important part of how we go to market," said Joby Executive Chairman Paul Sciarra. Sciarra said additional military users testing the aircraft will help Joby improve manufacturing, flight operations and other functions before it launches a taxi service to the public, a milestone the company aims to hit in 2024.

Joby has been working with the Air Force for the past two years to test its prototype aircraft that transports four passengers at speeds up to 200 miles per hour and can fly 150 miles on a single charge. The lightweight vehicles aren't designed for combat and will be used mainly for military logistics including medical emergencies and transporting supplies. Sciarra said that the Army and Navy have also identified eVTOL aircraft as a "critical area of interest" although they are not part of the contract expansion announced Wednesday.

Like Archer Aviation Inc., Beta Technologies Inc. and other eVTOL competitors vying to remake urban transportation, Joby must surmount regulatory and logistical hurdles before taking off. In addition to earning commercial certification in the U.S. and the UK and ramping up manufacturing, Joby will have to work to prevent accidents like the one which occurred earlier this year in a remote testing facility near Jolon, California. The company said at the time that the incident would not impact the company's long-term plans because when craft broke in midair, it was traveling at well above the maximum speed it would fly in service.

Joby has a market cap of $3.68 billion and will report its second-quarter financial results Thursday.

Lizette Chapman reports for Bloomberg News.

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