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AMARI AIR BASE, Estonia — NATO's newest members are nervous.

Troops are being trained up and reinforced. A new "spearhead force" is in the works. Fighter jets are scrambling. Military maneuvering is ramping up amid mounting concerns that Russian President Vladimir Putin will broaden his gaze beyond Crimea and Ukraine to the Baltic nations.

Valdis Dombrovskis, vice president of the European Commission, warned that Russia was redrawing the map of Europe by force. Britain's Defense Secretary Michael Fallon last week said there was a "real and present danger" Russia's president would seek to destabilize Estonia, Latvia and Lithuania — all small NATO members with enough legitimate issues of disenfranchisement among their Russian minorities to make them prime potential targets for any Putin push.

Lithuania moved to reintroduce the military draft this week, days after its foreign minister warned Russia was "behaving aggressively" and posed a threat to countries beyond Ukraine.

NATO insists that it is ready to confront any threat. But with its new members airing more and more anxiety over aggressive moves from Moscow, the alliance is beefing up its deterrent capabilities. Its "Top Guns" have been put on notice, part of the alliance's around-the-clock Baltic Air Policing mission.

"They're normally quite heavily armed — all sorts of missiles and so on"

The importance of attention to the aerial front line has been underscored by a dramatic uptick in Russian incursions into European airspace — though analysts say the moves are mostly for intimidation.

"It's essentially a way of saber rattling," said Justin Bronk, an analyst at the London-based Royal United Services Institute. "It's pointing out how quickly Russia can get inside NATO airspace in those countries with powerful military aircraft and it's also, of course, a way for Russia to test NATO readiness and response levels."

Italy's Ambassador to Lithuania, Stefano Taliani, called the Russian airspace violations "a kind of war game," telling NBC News that NATO pilots "know the rules."

Still, he warned that "in the Baltic states, we must be ready."

That's why fighter jets forming "Quick Reaction Alert" teams are on standby 24/7 at its bases across Europe, ready to scramble and intercept Russian planes at a moment's notice.

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Spanish Commander Lt. Col. Enrique Fernandez Ambel said that just one month into his deployment at the Amari air base in Harjumaa, Estonia, his crews have flown more than 100 hours — and that the need for speed is ever present.

"We need to be airborne the sooner the better," Ambel told NBC News, saying his pilots can be in the air within five minutes. "Once the aircraft has been identified, we need to go let them know that we are here."

The message the pilots carry to offending Russian planes is simple, Ambel said: “We’re here, we’re watching you, and be careful. That’s it."

The pilots at Amari Air Base know that when the code "alpha scramble" horn sounds about an unidentified aircraft entering NATO airspace, it's time to suit up and literally run to their jets for a mission.

The sprint to get airborne has become second nature, according to Spanish fighter pilot Daniel Leal.

"We are just thinking about what kind of aircraft we will find up there," said Leal. "You don’t need to be thinking on the step by step — your mind is already in the sky.”

The pilots never know what they're going to find in the skies — but it's rarely a commercial aircraft that sets off the horns. It's often a Russian military plane flying without transponders, or one which has deviated from its flight plan, or without any flight plan at all. Sometimes it's multiple aircraft flying in formation.

NATO officials note that one thing the Kremlin's aircraft often have in common is a lot of firepower.

"They're normally quite heavily armed — all sorts of missiles and so on," Chief of staff of the Estonian Air Forces, Lt. Colonel Riivo Valge, told NBC News. "It's no secret that NATO and our air policing units are armed only very lightly, not to provoke anybody…but the other side is showing off their weaponry quite freely."

That doesn't scare Spanish pilot Lt. Joaquin Ducay de la Riva, who's been flying for seven years and Eurofighters for nearly four.

"Russia have incredible airplanes… but this is a sweet ride," he said, casting a glance at the sleek jet behind him.

Flying at top speed in a Eurofighter is "awesomeness," he said.

"It's definitely a Ferrari or even better than that," Ducay, 27, said with a smile. "I like fancy cars but this is way better than that…an incredible aircraft in all senses."

While locals at one point might have been annoyed by the noise of aircraft overhead, they're now grateful for the sonic booms which show NATO's air defense is ready, according to Ducay.

"The other day a [local Estonian] guy from the hotel actually approached us and said thank you," he said.

The response — and missions — are similar at NATO's Siauliai Air Base in Lithuania. The Quick Reaction Alert teams there have been training, testing their responses and also intercepting all kinds of planes and formations, according to Italian Detachment Commander Col. Marco Bertoli.

When the Russians don't respond to radio calls, he said, often an "exchange of eyeballs" or even a handwave will get the NATO pilots' message across.

“He knows that he has been intercepted, he knows that he has to follow the rules."