ŠIAULIAI AIR BASE, Lithuania — When NATO’s call came, the French fighter pilots scrambled with practiced urgency, already suited up to shorten their response times.

They dashed in vans to hangars where their prepped and armed Rafale jets awaited, clambered into the cockpits and fired up the engines, which puffed and screamed.

Within minutes of takeoff from the Šiauliai Air Base in Lithuania, they were over the Baltic Sea, first intercepting a Russian Il-20 reconnaissance aircraft and then tailing supersonic Russian bombers and their fighter escorts that neared the airspace of multiple NATO countries.

In a conflict situation, things could quickly get heated. But for the moment, with Russia and the military alliance at odds over Ukraine but not at war, pilots on both sides just watched and filmed each other — keeping their distance like wary tomcats with claws unsheathed, their missiles visible but not used.

One of the points of the posturing — in aerial ballets that take place away from public gaze hundreds of times a year — is to try to ensure that the frostiness between NATO and the Kremlin over Russia’s full-scale invasion of Ukraine doesn’t tilt into open hostility.

Commanders and pilots flying NATO air-policing missions on the eastern flank of the 32-nation military alliance say that their goal is to deter, not provoke. They believe their presence is reassuring for Baltic states — Estonia, Latvia and Lithuania — that border Russia and its ally Belarus but don’t themselves have airpower to fight off any Russian attack, if it ever came to that.

“It’s a game of cat and mouse, or rather cat and cat,” said Lt. Col. Alexandre, commander of a French air force wing of four Rafales that is sharing the Lithuanian base with another fighter detachment from Romania. Citing security concerns, the French military withheld the commander’s surname.

“We watch each other, scrutinize each other and try to make sure that it doesn’t go any further,” he said.

Alliance members take turns policing Baltic skies around the clock, seven days a week. The French inherited the building that now serves as their temporary headquarters from a Spanish detachment. They will hand it over to Italian replacements in August. Successive teams leave plaques and badges on a wall that records their passage.

NATO scrambles jets to identify and possibly take other action when Russian planes fly in Baltic airspace without switched-on transponders and without filing flight plans or communicating by radio with air traffic controllers.

“There are plenty of times in which, on purpose or not, they’re not really respecting the ICAO — the International Civil Aviation Organization — rules, regarding flight plans and behavior,” said Col. Mihaita Marin, commanding the Romanian detachment of six F-16s.

“So obviously we are forced to take off and just make sure that they are who they say they are and their intention is peaceful,” he said.

The arrival of spring, bringing better flying conditions, means French and Romanian flyers have been busy since they deployed at the start of April on four-month NATO rotations.

Marin said interceptions “are getting close to daily” and “that will definitely increase as the weather is getting better.”

French aircrews — watched by an Associated Press journalist who was reporting at the airbase — had their busiest day so far on Monday.

Scrambled under NATO command, French Rafales met and observed a pair of Russian Tu-22M3 bombers carrying supersonic, anti-ship missiles from their bellies that Russia has also used in Ukraine, repurposing them to attack ground targets, and which can be equipped to carry a nuclear warhead.

The strategic bombers’ more than four-hour flight from an airbase near St. Petersburg, escorted by Su-30 and Su-35 fighters, remained in international airspace but took them past the coasts of NATO countries Finland, Estonia, Latvia, Lithuania and Poland, doubling back when they approached Denmark.

The French detachment said the Russian planes didn’t have switched-on transponders, file flight plans or enter into radio contact. Fighter jets from Sweden, Finland, Poland, Denmark and Romania also went airborne to keep watch, according to the French. NATO didn’t respond to requests for comment.

The French commander, Lt. Col. Alexandre, said it isn’t clear why Russian pilots behave in ways that could endanger other users of Baltic airspace.

“We don’t know if it’s lack of professionalism or just a means for them to test us,” he said.

“But what is sure is that we need to go every time,” he added. “We cannot say, ‘OK, that’s usual, this time we will just let them pass.’”