A Ukrainian International Airlines flight that crashed in Iran Wednesday, killing all 176 people on board, was likely shot down by Iranian forces, U.S. intelligence suggests.

While the crash of Flight 752 is a tragedy, the likely cause of the crash might not be entirely surprising, given the flurry of threats and tit-for-tat attacks exchanged between the Untied States and Iran over the last week. While civilian air travel is considered to be very safe, there is a long history of civilian aircraft being accidentally shot down in times of conflict.

“I don’t think it’s all that unusual,” Arnold Barnett, an aviation safety expert and a Professor of Statistics at the MIT Sloan School of Management, tells TIME. “I think given that war so often involves aerial fighting these days, you could argue that planes should be careful.”

In fact, both Ukraine and Iran have their own tragic histories of civilian aircraft being shot down during geopolitical conflicts. In July 2014, 298 people were killed when Malaysian Airlines Flight 17 was shot down in Ukraine’s Donetsk region by Russian separatists. In 1988, 290 people were killed when a U.S. ship shot down Iran Air Flight 655.

Barnett argues that airlines should err on the side of caution when considering the threat of sending flights through conflict zones — and urges civilian passengers to pay attention to warnings from the U.S. State Department and elsewhere.

“Planes being shot down accidentally—this is not something that’s never happened. And especially in wartime situations where you think it might happen, of course I think people should be thinking about it,” Barnett says.

Here’s what you need to know about some of the deadliest attacks on civilian aircraft.

Libyan Arab Airlines Flight 114 (Feb. 21, 1973)

More than 100 people were killed when a Libyan flight traveling from Tripoli via Benghazi to Cairo was shot down by Israeli fighter planes and crashed into the Sinai desert. The aircraft was about 100 miles off course, Major John T. Phelps II wrote in the U.S. Armed Forces journal Military Law Review.

Israel claimed the plane had entered Israeli airspace in Egyptian territory occupied by Israeli, and that the Israeli planes had directed the aircraft to land, but that the plane did not respond.

A co-pilot who survived the crash later said the plane had known that the Israeli planes had asked them to land, but they had decided not to because of the bad relationship between Libya and Israel, although the inflight record indicated that the pilot thought he was in Egypt and that the other planes were Egyptian, Phelps wrote.

Phelps asserted that the Libyan jet’s actions were likely viewed as “hostile” by the Israeli forces.

“The situation in the Sinai was anything but normal. Relations between Egypt, Libya, and Israel were tense and the threat of war was ever-present,” Phelps wrote.

Korean Air Lines Flight 007 (Sept. 1, 1983)

During some of the tensest moments of the Cold War, a Soviet fighter plane shot down Korean Air Lines Flight 007, which had been traveling from New York to Seoul via Anchorage, Alaska. All 269 people on board, including U.S. Congressman Larry McDonald, were killed. The flight had traveled more than 300 miles off course and ventured into Soviet airspace, where it was shot down near Moneron Island west of Sakhalin Island. It crashed into the Sea of Japan.

The Soviets asserted that the aircraft had been sent on a spy mission, and that the plane had deliberately been sent into Soviet airspace, the New York Times reported. The U.S. denied that assertion.

Iran Air Flight 655: (July 3, 1988)

In the midst of the Iran-Iraq war, the U.S. and Iran had just faced off in Operation Praying Mantis, a daylong naval battle between American forces and Iran in the Persian Gulf, which had been triggered by a U.S. ship striking an Iranian mine.

U.S. Navy missile cruiser USS Vincennes shot down Iran Air Flight 655 traveling from Bandar-e Abbas, Iran, to Dubai, UAE, as it traveled over the Strait of Hormuz, a strait between the Persian Gulf and the Gulf of Oman. All 290 people on board died. The passenger plane, which was traveling in Iranian airspace, had been misidentified as a fighter jet, according to the United States.

While the U.S. asserted that the plane was outside the civilian corridor, this proved to be untrue. The U.S. government later apologized and after eight years said it would compensate the victims’ families, according to the Associated Press.

Siberia Airlines Flight 1812: (October 4, 2001)

Not all airliner shoot downs have occurred during times of war. The Ukrainian Air Force shot down Siberia Airlines Flight 1812 over the Black Sea in an apparent accident, killing 78 crew and passengers. The flight had been en route from Israel to Novosibirsk, Russia, and many of the passengers were Russian-born Israelis, according to the Associated Press.

Ukraine’s military initially denied responsibility for the incident, but later admitted that an errant missile from a military exercise on the Crimean peninsula could have cause the crash. Ukraine’s Defense Minister, Oleksander Kuzmuk, admitted that Ukrainian forces were involved and apologized to the victims’ friends and families.

Malaysia Airlines Flight 17: (July 17, 2014)

In 2014, Ukraine was again the site of tragedy—this time, in the midst of conflict with Russia. Russian separatists shot down Malaysia Airlines Flight 17 as it traveled over the Donetsk region in Eastern Ukraine, killing all 298 people onboard. A subsequent investigation found that the plane had been downed by a warhead launched in eastern Ukraine by a Buk missile system.

The Public Prosecution Service of the Netherlands announced last June that it will prosecute four suspects—all affiliated with Russian separatists—for causing the crash and murdering the people on board.

Russian officials have denied playing a role in the crash.

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