San Francisco skygazers noticed an unmarked and very large white blimp flying at an impressive speed above the city Thursday afternoon. It appears to be Google co-founder Sergey Brin’s new blimp, which is the biggest blimp since the Hindenburg.

Between about 1pm and 2pm on Thursday afternoon, many San Franciscans looked to the skies and collectively declared, “WTF is up with that big white blimp up there?” After all, there are no sporting events happening in SF today, and the completely unmarked white blimp appeared to be unusually large, and traveling at an exceptionally rapid speed (for a blimp, at least.)

Our curiosity aroused, SFist looked it up on the flight tracking tool ADS-B Exchange to figure what was up with this hauling-ass blimp. The blimp’s flight data as of 2:15 pm is seen below. Tracking the blimp, it reached reported speeds as high as 30 knots per hour, which is the equivalent of about 35 miles per hour.

Image: ADS-B Exchange

And very tellingly, the blimp is shown as registered to a LTA Galactic, Inc. That’s the registered name for the company Lighter Than Air Research, established by Google co-founder Sergey Brin, and described by Business Insider as making “Sergey Brin's 'air yachts.'”

It appears the same blimp was spotted Wednesday by NBC Bay Area’s Raj Mathai. “Pathfinder 1 (double the size of @goodyear Blimp). Landing at its base: Moffett Field (along 101 in Mountain View),” Mathai posted. “‘Lighter Than Air’ ship from LTA Research (funded by @Google co-founder Sergey Brin).”

Turns out we’d been warned this thing would be flying over our skies. SFGate reported in mid-November that Pathfinder 1 was beginning test fights, noting that the craft is “the largest aircraft since the Hindenburg.” But things should not end as badly for Brin’s Pathfinder 1 as they did for the Hindenburg, as per SFGate, the “patented material covering its 13 giant helium bags is non-flammable.”

Image: ADS-B Exchange

As of press time for this post just after 3 pm PT, the blimp appears to be back at Moffett Field in Mountain View. Keep an eye out if it decides to make more flights!

Related: Amazon Patents Floating Blimp Warehouse For Drone Deliveries [SFist]

Image: @joe_m26 via Twitter