The Syrian Armed Forces have warned the U.S. of “serious repercussions” after a Boeing F/A-18E Super Hornet belonging to the U.S. Navy shot down a Syrian Sukhoi Su-22.                                                                       

The Soviet-era ground attack aircraft had dropped bombs close to U.S.-backed Syrian Democratic Forces (SDF) south of the town of Tabqah in Syria on June 18 and was “immediately shot down” by the Super Hornet, the Pentagon said.

The single-seat F/A-18 had been patrolling the area after Syrian government-backed forces attacked an SDF position in Ja’Din earlier in the day.

The Syrian government decried the incident in a statement and confirmed “the loss” of the Su-22 pilot. The Russian Ministry of Defense says in its own statement that the pilot ejected, but his fate is unknown.

The incident marks the first U.S. air-to-air takedown of a manned Syrian warplane since the U.S.-led intervention in Syria to combat the Islamic State terrorist group began in September 2014.

The shootdown comes after a U.S. Boeing F-15E Strike Eagle intercepted and destroyed an armed UAV controlled by “pro-regime forces,” which had been threatening U.S.-backed forces fighting in Syria on June 8. The UAV was reported as an Iranian-made Shahed-129, similar in size to the MQ-1.

In a statement about the Su-22 intercept, the combined joint task force leading Operation Inherent Resolve (CJTF-OIR) said in a statement that the U.S.-led coalition operating in Syria “will not hesitate” to defend itself or partner forces from any threat. It stresses that the coalition is not looking for a fight with forces loyal to Syrian President Bashar al-Assad or his Russian backers, but would act if necessary.

The air-to-air engagement occurred at about 6:40 p.m. local time. Coalition aircraft were conducting a “show of force” against pro-Syrian regime forces that had been advancing on Ja’Din earlier 2 hr. earlier.

Russia was contacted by the U.S. via an established “deconfliction  line” prior to the Su-22 shootdown to try to de-escalate the situation, CJTF-OIR says.

Russia called the Su-22 shootdown a “cynical violation” of the Syrian Arab Republic’s sovereignty and claims proper deconfliction procedures were not followed. Moscow says that from now on, coalition aircraft flying west of the Euphrates River will be considered potential targets by Russian aircraft and surface-to-air missiles.

The Syrian government said in a statement that its aircraft crashed in the Resafa region of Syria. Damascus maintains its forces were targeting terrorists in the area and directly accuses the U.S. of supporting Daesh, the local name for the Islamic State.

This is the latest in a string of run-ins between U.S. and Syrian forces, the most spectacular being President Donald Trump’s Tomahawk cruise missile strike on Shayrat Airbase in April in retaliation for chemical weapon attacks on civilians by Syrian forces.

That attack, involving 59 missiles fired from U.S. Navy warships, destroyed several Su-22 and Mikoyan-Gurevich MiG-23 aircraft of the Syrian Arab Air Force.

Despite more than 25 years of continuous U.S. military engagement in the Middle East, air-to-air engagement is quite rare. Dozens of remotely pilot aircraft have been shot down by various sides, but intercepts of manned warplanes by fighters have been minimal.

A Turkish Air Force F-16 sparked a diplomatic dispute in November 2015 when it shot down a Russian Sukhoi Su-24 conducting operations along the Syrian-Turkey border. The Russian pilot died and two Mil Mi-8 helicopters also came under attack.

Russia and Turkey have since mended ties.