Was a Ukrainian Passenger Plane Lost in the Fog of War?

If Iranian anti-aircraft missiles took down a Ukrainian jetliner this week, as U.S. intelligence suggests, the 176 people killed on-board have become the latest victims claimed in the fog of war. Ukraine International Airlines Flight 752 took off from Tehran and went down minutes later — and just two hours after the Iranian military launched a ballistic missile attack on Iraqi bases housing U.S. soldiers.

Three U.S. military and intelligence officials tell TIME they now are confident that the plane, bound for Kyiv, was hit by two Iranian anti-aircraft missiles fired Thursday from a site outside Tehran. The officials, who were not authorized to speak publicly on the matter, said a definitive conclusion awaits data from the Boeing 737-800’s Cockpit Voice and Flight Data Recorders. But some of the same U.S. intelligence satellites and assets that detected the missile attack on the Iraqi military bases, also picked up Iran’s air defense systems turning on radar and launching surface-to-air missiles.

Secretary of State Mike Pompeo confirmed the assessment in a press conference at the White House on Friday. “We do believe that it’s likely that that plane was shot down by an Iranian missile,” he said. “We’re going to let the investigation play out before we make a final determination… When we get the results of that investigation, I am confident when we and the world will take appropriate actions in response.”

It remains unclear how the Iranian military might have mistakenly shot down a massive jetliner that had departed a major commercial airfield and was following a flight plan that had been filed with aviation authorities. The plane lifted off from Tehran’s Imam Khomeini Airport, and climbed to an altitude of about 7,900 feet before abruptly stopping transmitting data two minutes after take-off, according to the flight-tracking site Flightradar24. Video footage, verified by The New York Times, appears to show at least one missile hitting the plane, which attempts to return to the airport before an immense fireball spreads briefly across the pre-dawn sky.

Some U.S. officials believe the jet was shot down unintentionally. “All indications are that the passenger jet was hit by mistake, likely because the Iranian air defenses were on a state of high alert as they launched a barrage of ballistic missiles at U.S. facilities,” a U.S. official told TIME. Photographs allegedly taken of the crash site and shared widely on social media appear to show a piece of an SA-15 Gauntlet, a Russian-made anti-aircraft system that Iran added to its arsenal beginning in 2007.

While the U.S. government has yet to go public with evidence to support its assessment of an accidental shoot-down, military and intelligence officials tell TIME that advanced U.S. satellites played a key role in intelligence officials’ determination that two surface-to-air missiles hit the plane.

U.S. spy satellites equipped with infrared sensors and high-resolution cameras maintain near constant surveillance of major Iranian military facilities, and the National Security Agency uses electronic eavesdropping equipment to monitor Islamic Revolutionary Guard Corps and other Iranian communications. In addition, the U.S. maintains radar stations in Iraq to detect incoming Iranian missiles and aircraft.

Every moment of every day, the Space-Based Infrared System is designed to identify within seconds the location of a missile’s launch site, trajectory and potential target. A constellation of school bus–sized satellites, known as the Defense Support Program, forms the backbone of the system. These so-called early warning satellites are armed with cutting-edge infrared sensors and instruments that operate at wide angles to detect heat signatures from missile plumes as they flash against Earth’s background.

In addition, the U.S. operates a wide range of sensors that scour the Earth for electronic emissions from foreign nations’ defense systems so that analysts can sift through the data and determine the origin of the signals and weapon type. For instance, the SA-15 Gauntlet system uses a specific radar array to search, acquire and track targets. After an anti-aircraft missile is fired, it also emits a radar signal to hone on a target.

A combination of all this intelligence gathered over a period of seconds or minutes would allow the 460th Operations Group at Buckley Air Force Base in Colorado to triangulate the point of launch and track the trajectory of the missile, much of it under a method of spy-craft known as measurement and signature intelligence, or MASINT. The information would be relayed to the Pentagon and commanders on the ground to make decisions of how to respond.

The Pentagon, CIA and Office of the Director of National Intelligence all declined to comment on Thursday whether their analysts had concluded that Iran shot down the plane. Going public with the information has its risks in trying to mitigate damage with Tehran, considering tensions have eased considerably since Thursday’s Iran’s missile strike. President Donald Trump said the incident had “nothing to do with us… Someone could have made a mistake on the other side.”

Nevertheless Trump’s order to kill Iranian Major General Qasem Soleimani in a Jan. 3 drone strike contributed to the developments that brought both nations to the brink of war. And it would not be the first time a military mistakenly downed a commercial jet during heightened military tensions.

Despite all the high-tech wizardry of modern warfare, human nature makes war messy. Military analysts describe a “fog” that sets in over the battlefield, making it difficult to rationally make decisions or assess facts, often resulting in miscalculation that results in unforeseeable consequences.

In 1988, the U.S. Navy warship Vincennes mistakenly downed Iran Air Flight 655, carrying 290 people. Five years earlier, a Soviet fighter plane shot down Korean Air Lines Flight 007, carrying 269 people, including a U.S. congressman.

“How can it happen? The crew talked themselves into things that simply were not true,” said John “Fozzy” Miller, a retired Navy admiral and former commander for U.S. naval forces in the Persian Gulf, referring to the USS Vincennes incident. “It’s not because they had the wrong intent. It’s because they felt like they could be under attack… and you just begin to see things that really aren’t there.”

Miller, who’s now an associate fellow for the International Institute for Strategic Studies, cited the post-accident investigation done by the Navy that pointed to a kind of “group psychosis” that gripped the ship’s crew that was constantly scanning the skies for an Iranian attack. Even when using sophisticated anti-aircraft systems, like the Vincennes’ then-state-of-the-art Aegis Weapons System, a scared crew “can override all of that sophisticated information, and see something as an enemy target,” Miller said.

Iran, for its part, has denied that its forces carried out the shoot-down, whether by accident or otherwise. Despite these denials, Ukrainian investigators say they are considering a missile strike or an act of terrorism as possible theories for the plane’s destruction.

Fred Kagan, director of the Critical Threats Project at the right-leaning American Enterprise Institute think tank, says it would be a “humiliation” if Iran proves to have shot down a commercial jet with dozens of its own citizens onboard.

“It badly undermines their image of professionalism and quality of the air defense force around Tehran, which you would have thought are the best and most reliable forces they have,” he told TIME Thursday. “Now they have to decide whether they are going to cop to this and apologize to the Ukrainians for shooting down their plane, and if they don’t do that, then they have isolated themselves further.”

Although the U.S. and Iran have stepped back from the precipice of war, the environment between the two nations remains tense, says Phillip Carter, a former Obama administration official now with the RAND Corporation. “In a perfect world, an air traffic controller or air defense operators could distinguish between friend and foe and tell one aircraft from one another,” he says. “But this was a tense situation and radar signatures can be hard to interpret when under stress.”