4 times in 4 days: Russian military aircraft fly off US coast

The Alaskan Air Defense Identification Zone is a designated region of international airspace, primarily surrounding the US and Canada, that is meant as a buffer to allow for the identification of aircraft heading towards North America.

While these flights pose no real military threat, US defense officials are taking notice of the high frequency at which they've occurred this week.

There is "no other way to interpret this other than as strategic messaging," one official told CNN.

While the Russians have not conducted flights of this nature since 2015, another senior defense official stressed that they are "not a concern" and attributed the uptick to a recent lack of available Russian aircraft and need to boost training.

"We haven't seen this sort of level of activity for a couple of years," said John Cornelio, a NORAD spokesperson, though he emphasized it was not "unprecedented" or "unusual."

This "shows the value of NORAD and that binational US and Canada relationship," he said, pointing to the two nations working together to identify and intercept the Russian long-range aircraft.

Earlier in the week, US defense officials called recent sightings of the bombers "nothing out of the ordinary" -- itself an indication that both nations are toeing the line between routine military posturing and escalating provocation.

On Monday, US F-22 fighter jets intercepted two Russian bombers in international airspace 100 miles from Kodiak Island, Alaska. A US military official called the interaction "safe and professional."

Less than 24 hours later, a US surveillance aircraft responded to two Russian bombers that were spotted in the same area, this time flying 41 miles off Alaska.

The US itself has carried out similar flights along both the Chinese and Russian coasts.

Moscow, for its part, said it "regularly carries out patrol missions above the neutral waters of the Arctic, the Atlantic, the Black Sea and the Pacific Ocean."

"All such missions are carried out in strict compliance with international regulations and with respect to national borders," the Russian Defense Ministry said in a written statement.

But this week's encounter plays into a larger effort by Russian President Vladimir Putin "to prove Russia is back in the game," according to Howard Stoffer, a former State Department staffer.

"This kind of cat-and-mouse stuff has been going on for a while now," Stoffer told CNN, adding that Putin "is trying to put the US on notice that the Russians are everywhere and are back to expanding the limits of expanding their military power."

"It is one thing when you fly to be noticed," he said. "When the Russians buzz US ships, that is an unprofessional action because upsets the operation and is dangerous for all parties involved ... that is where the line that is drawn."

US officials have echoed Stoffer's stance as recently as February, after the USS Porter had three encounters with Russian aircraft while sailing in the Black Sea.

Those encounters were deemed unsafe and unprofessional because of how close the Russian planes flew to the American destroyer, a senior defense official said at the time.

Moscow denied that its aircraft had made any unsafe moves.

Russian aircraft have also been spotted recently flying near the coastline of US allies, including Japan, which has scrambled fighter jets four times this month in response, according to a statement from the Japanese Foreign Ministry.

The Viktor Leonov, a Russian spy ship, has also been spotted near the US coastline twice in recent months.

Rising tensions between US and Russia are a far cry from President Donald Trump's optimistic campaign rhetoric of hopes for a collaborative relationship. As Trump himself said earlier this month, relations between the former Cold War foes "may be at an all-time low."

The two nations have clashed over deeply rooted strategic differences this month.

Syrian President Bashar al-Assad's alleged April 4 chemical weapons attack on his own civilians triggered Trump's outrage, leading him to strike a Syrian airfield with Tomahawk missiles, and witnessed a change in Trump's stance on Russia, which has supported Assad throughout Syria's bloody civil war.

Russian Foreign Minister Sergey Lavrov said that the US missile strikes on an airfield in Syria were a failed attempt to try to undermine the peace process in the country and to change the regime.

And Russia has stood with Iran, a long-time US foe, in condemning the strikes.

"Attempts of this kind will never be a success. It will never happen," Lavrov said during a joint news conference with the Iranian and Syrian foreign ministers in Moscow. "We demand that the United States should respect the sovereignty of a state and avoid such actions that threaten the current world order."

Opposing views on the conflict in Ukraine have also become a hot-button issue between the Kremlin and the new US administration.

In February, Russia's Foreign Ministry also indicated that it intends to keep Crimea and not return it to Ukraine because it considers it to be part of Russia -- a stance that the Trump administration has said it directly opposes.

White House press secretary Sean Spicer said earlier this year that Trump had been taking a tough line with Russia and that he expected Moscow to withdraw from the region, which it has occupied since 2014.

The US, meanwhile, has positioned military assets across Europe in an effort to reassure its European and NATO allies in the wake of Russia's movements in Ukraine.

Over the weekend, the US Air Force sent its newest stealth fighters to the United Kingdom in a demonstration of its military reach.

This week's encounters might be routine military chest-thumping, but the countries' entwinement in complex military situations around the world raises the risk of escalation.

American forces have so far refrained from engaging Russian aircraft after they've performed maneuvers like buzzing Navy ships. But Stoffer indicated retaliation could be possible in the future.

According to Stoffer, it is unlikely that the US would go to the extreme of firing a shot across the bow of a Russian ship or shooting down a Russian jet carrying out an unsafe move.

But he could see a scenario in which a US commander greenlights alternative responses like jamming the aircraft's radar and avionics systems -- which could cause the aircraft to crash.

If a minor provocation were to escalate and turn into a larger-scale war situation, Moscow would be at a disadvantage, according to retired Air Force Gen. Michael Hayden.

"No one wants to go to war with the Russians, but let me double down on another concept: The Russians really don't want to go to war with us," said Hayden, the CIA and National Security Agency director under President George W. Bush, during an interview on CNN's "Erin Burnett OutFront."

"They are by far the weaker power," he said.