New satellite images of the Tonopah Test Range in Nevada have spurred the interests of conspiracy theorists and aviation nerds alike, thanks to what appears to be a blurred out portion of a secret aircraft sticking out of one of the hangars. Simply censoring a small portion of satellite images of a military installation alone may not have been enough to get the internet’s mouth watering, but the Tonopah Test Range has a long and illustrious history of harboring secret military aircraft within its expansive hangars — from the F-117 Nighthawk (long before it was acknowledged by the U.S. government; sometimes called the Stealth Fighter) to secret Soviet Migs used for testing.

It also happens to be a part of the massive Nellis Range — a huge stretch of territory used for all sorts of military purposes, including housing an installation which popular culture has taken to calling “Area 51.”

These new images compound previous satellite pictures confirming the construction of a new large-scale hangar at the above-mentioned “Area 51” from last year, begging the question: what kind of secret aircraft is the Defense Department testing out in Nevada?

By their very nature, these secretive projects are, well, a secret — but there are some clues floating around the veritable sea of government contracts and defense technology firms. Here are just some of the aircraft that are currently rumored to be under development or even already in testing. Some of these programs are publicly acknowledged, while others are the products of informed speculation… but all seem like potential tenants for these highly secretive hangars.

Lockheed Martin SR-72

The SR-71 Blackbird remains the fastest operational military aircraft the world has ever seen, with a top speed that exceeded Mach 3. Today, Lockheed Martin is already working on a worthy successor for the nameplate in the form of the SR-72 project: a ramjet-powered aircraft that aims to achieve and maintain hypersonic speeds — or speeds in excess of Mach 5. Currently, only missiles have managed to operate at that velocity.  It’s no secret that this aircraft (which would almost certainly be unmanned because of the speeds at which it would travel) is under development at Lockheed Martin… but what really got the attention of internet sleuths were remarks made by Lockheed’s Vice President, Jack O’Banion, late last year. O’Banion showed an artist’s concept of the SR-72, and then said this:

Without the digital transformation, the aircraft you see there could not have been made. We couldn’t have made the engine itself — it would have melted down into slag if we had tried to produce it five years ago. But now, we can digitally print that engine with an incredibly sophisticated cooling system integral into the material of the engine itself, and have that engine survive for multiple firings for routine operation.”

That language certainly does make it seem like Lockheed Martin has already built at least a technology demonstrator for their SR-72 concept — a demonstrator that’s got to fly out of somewhere if it does exist.

Northrop Grumman B-21 Raider

The B-21 Raider is certainly no secret, with even China recently offering up a sneak peek of their own forthcoming stealth bomber in a video that was clearly meant to poke some fun at the U.S.’ planned deep penetration bomber. Nonetheless, few details about the B-21 have made their way to the public, despite claims that the bomber will enter into service by the mid-2020s. That means this bomber, which as far as the American people are aware, exists only in the form of a single artist’s rendering, is expected to be dropping live ordnance on America’s enemies within the next seven years.

One might think they’d want to start building these things pretty soon then. The last time Northrop Grumman offered up any details regarding the B-21’s development at all, it was to say that they had completed wind tunnel testing months ago. Since then, the program’s office has offered nothing but assurances that the program is continuing on schedule and on budget.

“There are adversaries out there that want to know what we’re doing, and are probably going to great lengths to try to get to that level of insight,” said the executive officer of the Air Force Rapid Capabilities Office, Randy Walden. “We’re doing everything we can to prevent that.”

Large Scale Strike and Electronic Attack Drone

For years, rumors have persisted about a military drone that bears a striking resemblance to Lockheed Martin’s RQ-170 (shown above) but on a much larger scale. Based on an analysis of the satellite images of the Tonopah Test Range conducted by Tyler Rogoway at the Warzone, the blurred out craft shown in the pictures seems to have a wingspan of about 80 feet. The RQ-170’s wingspan is about 66 feet, so the craft in the image could potentially be its mythical big brother.

Because this isn’t an acknowledged project from the U.S. Defense Department or Lockheed Martin, there’s no proof that such an aircraft exists — but the rumors claim it was designed as a strike and electronic warfare platform. With new unmanned aerial vehicles hitting the market every day, it seems possible that the Pentagon might have one or two that have yet to make their official debut on the world’s stage.

Foreign Aggressor Aircraft

Aggressor squadrons (or adversary squadrons) are aircraft squadrons made up of pilots and aircraft trained specifically to serve as a stand-in for enemy forces in training situations. Often, these squadrons are made up of domestically sourced aircraft that can approximate the behavior of enemy planes (like the Navy’s Top Gun school employing the A-4 Skyhawk as a stand-in for the Mig-17 in the late 1960s), but every once in a while, the DoD manages to get its hands on the real thing.

On these rare occasions, the Pentagon sets about doing two things: keeping their acquisition a secret and working to find out exactly what the enemy’s aircraft are capable of. There aren’t many new fighters operating in the world that the United States would be looking to get its hands on, and many of the newest ones don’t exist in enough numbers to have any misplaced. China’s J-20 program and Russia’s Su-57 program have yielded so few jets combined that you could almost count them all on two hands… making it extremely unlikely that Uncle Sam might get his mitts on any of them.

However, some advanced fourth-generation fighters, like Russia’s Su-35 or even their carrier based Su-33 (which also serves as the loose basis for China’s J-15) could be extremely valuable to the U.S. for study. Based on the blurred wing-shape shown in the satellite image, these platforms seem like unlikely candidates for the satellite image that’s caught the internet’s attention this week, however.