Mountain View-based Reliable Robotics has secured an additional $115 million in financing, expanding its Series D round from $160 million to $275 million and pushing its valuation above $1 billion.
The new financing includes approximately $90 million in equity and a $25 million term loan from Silicon Valley Bank.
Nimble Partners led the investment, with participation from Gideon Capital, RockCreek, Geek Ventures, Gold Hill Capital, Sparkwave Capital and other investors. The company reports having raised more than $380 million in equity capital to date.
Founded in 2017 by CEO Robert Rose and CTO Juerg Frefel, Reliable is developing autonomous flight systems designed to be installed on existing aircraft.
Rose previously worked on flight software at SpaceX and autonomous vehicle technology at Tesla, while Frefel spent years developing aerospace systems at SpaceX.
Unlike startups building entirely new aircraft, Reliable is focused on automating the planes that airlines and cargo operators already use.
Its Reliable Autonomy System is designed to automate flight operations from engine startup and taxiing through takeoff, en-route navigation and landing.
The initial target aircraft is the Cessna 208B Grand Caravan, a widely used aircraft for regional passenger and cargo operations.
Reliable's strategy is built around certification. Commercial aviation requires new flight-control systems to meet extensive Federal Aviation Administration safety requirements before they can be deployed at scale.
The company has made progress toward FAA approval of its continuous autopilot engagement system, designed to automate flight operations while a pilot remains onboard.
Reliable is also developing a separate solid-state radar system for detecting obstacles and other aircraft. The technology uses electronic scanning rather than mechanically moving antennas.
Its long-term goal is to enable aircraft to operate without a pilot physically present in the cockpit, supported by remote supervision and certified autonomous systems.
The company is pursuing multiple related certification processes, covering onboard automation, remotely supervised operations, radar technology and the airline operations needed to commercialize its systems.
Reliable has also established its own cargo airline operation, Reliable Airlines, based in Albuquerque, New Mexico. According to TechCrunch, the operation uses six Cessna Caravans to transport cargo six days a week.
Operating aircraft provides the company with direct experience in airline logistics, maintenance and operational requirements while it develops its autonomous technology.
Reliable has also secured relationships with US military organizations and is participating in an FAA aviation integration pilot program supporting cargo operations in New Mexico and Colorado.
The latest funding will expand its aircraft fleet, production capacity and engineering team. The company is also opening offices in Seattle and San Diego and reports employing more than 250 people.
The economic opportunity is particularly relevant for regional aviation. Smaller cargo routes can be expensive to operate, and automation could eventually improve aircraft utilization and reduce operating costs.
However, Reliable faces one of the most demanding regulatory pathways in technology.
Certification timelines remain uncertain, and the benefits of autonomous flight depend on more than removing a pilot from the cockpit. Operators must consider equipment costs, remote supervision, maintenance, insurance and ongoing regulatory requirements.
Reliable has made substantial technical and regulatory progress, but its full commercial model remains dependent on certification.
The next milestone is demonstrating that its automation systems can move from development and testing into approved, repeatable airline operations.