U.S. Defense Secretary Jim Mattis is questioning whether recent close encounters between Russian and U.S. warplanes over Syria were mistaken or the result of what he called "dangerous" maneuvers by some Russian fighter-jet pilots.
"Right now, I cannot tell you if it's sloppy airmanship, rambunctious pilots, or people who are trying to do something that is very unwise," Mattis said in remarks to Pentagon reporters on December 15.
A day earlier, the Pentagon said that two Russian Su-25 fighter jets flew through an unofficial line separating Russian and U.S. air forces in eastern Syria on December 13 and came dangerously close to U.S. warplanes.
During the incident, the Pentagon said U.S. Air Force F-22 fighter jets launched warning flares and deployed chaff -- used to distract potential incoming missiles.
The U.S. pilots also radioed the Russian pilots multiple times on an emergency channel demanding that they leave the U.S. portion of the air space over a Syrian safe zone that had been negotiated in an agreement between Russian and U.S. forces, the Pentagon said.
The Russian Defense Ministry on December 14 denied that its pilots were at fault, saying Russia's jets did not cross the unofficial boundary line, and claiming the U.S. jets eventually left the region after another Russian jet, a Su-35C, arrived.
The Pentagon on December 15 said other close calls have occurred when Russian jets flew over the same dividing line, which runs along with Euphrates River, into the area east of the river designated as U.S. airspace without notifying U.S.-led coalition forces ahead of time.
Lieutenant Colonel Damien Pickart, an air force spokesman in the Middle East, said in an e-mail to AFP that on November 15, two U.S. A-10 Warthog ground-attack planes nearly collided head-on with a Russian Su-24 Fencer that passed within only 90 meters of the U.S. planes.
One A-10 pilot had to "aggressively execute a defensive maneuver to avoid a midair collision," Pickart told AFP.
Then on November 17, he said two F-22s intercepted an armed Russian Su-24 that flew over coalition and partner forces three times and failed to respond to radio calls.
"The F-22s intercepted this pilot and were in a position to fire," Pickart told AFP.
"Luckily our pilots showed restraint, but given the actions of the Su-24 aircraft could have reasonably been interpreted as threatening to U.S. forces, our pilots would have been well within our rights to engage," he said.
"The coalition's greatest concern is that we could shoot down a Russian aircraft because its actions are seen as a threat to our air or ground forces," Pickart told AFP.
"We are not here to fight the Russians and Syrians -- our focus remains on defeating [the Islamic State extremist group]. That said, if anyone threatens coalition or friendly partner forces in the air or on the ground, we will defend them."
Mattis said it was not clear if the incidents were accidental and due to the inexperience of the young pilots, or deliberate and the product of those pilots "dangerously feeling their oats."
"I don't expect perfection, but I don't expect dangerous maneuvers either, and so we'll sort this out," he said at the Pentagon.
Mattis said that the United States and Russia were still using a hot line to try to avoid such close calls as each country's warplanes operate in often close proximity in Syrian airspace.