Largest aircraft in the world seen over US. What is it doing?

The large airship recently spotted in California is Pathfinder 1, billed as "the world's largest aircraft" and built by the LTA Research Company. At 406.5 feet long and 66 feet wide, Pathfinder 1 falls into a category of airships called "lighter-than-air" or LTA aircraft. For comparison, a Goodyear blimp is 246 feet long.

LTA includes blimps—such as the famous Goodyear Blimp, which celebrates its 100th anniversary in 2025—but also balloons and powered airships.

Pathfinder, which is not specifically a blimp, aims to distance itself from the prevailing public perception of the 1937 Hindenburg disaster, according to J. Gordon Leishman said its development and testing around the Bay Area raises an interesting question for the future of airships.

He said that to have a viable future in the industry, airships will have to compete with more established methods of transporting goods or people, but they have some advantages that could make them useful.

He said, "Lighter-than-air aircraft technologies like airships have some interesting possibilities for what they can contribute to the world of aviation."

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Leishman said that lighter-than-air aircraft are any aircraft that generate buoyancy using a gas with a density lower than air. A blimp is essentially a gas-filled envelope, while other types of airships have some internal structure; they are called dirigible or semi-rigid airships. Pathfinder 1 is a rigid airship, not technically a blimp.

There aren't many blimps flying around the world these days, and if you see one, it's easy to tell what it's doing—usually advertising for companies like Goodyear or DIRECTV or creating aerial footage of sporting events. So when San Francisco residents saw Pathfinder 1 floating near the Golden Gate Bridge, they must have wondered what it was doing.

Leishman said that Goodyear blimps are no longer full-fledged blimps; they're more like semi-rigid airships. It first announced in May that it had successfully flown the vessel outside the airfield at Moffett Federal Airfield, which once housed blimps and balloons for the US military.

Pathfinder previously conducted both tethered and untethered tests at the airfield in Mountain View, California, outside San Francisco. Last month, the company said it had received permission to fly Pathfinder to test long-distance flights over a large area around San Francisco.

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Leishman said airships have long had a bad reputation for being "large, bulky, and unsafe." The Hindenburg accident, when an airship caught fire while landing in New Jersey after carrying passengers across the Atlantic,