
Reuters
Moscow is calling it a "planned provocation." Turkey, a member of the NATO alliance, has said it had a right to defend its airspace.
But there's a big reason Russia and President Vladimir Putin would choose against severely escalating the situation in response: The many economic ties between the two countries.
"Putin's ability to be pragmatic economically should not be underestimated. Let's keep in mind, Russia is still providing gas to Ukraine …and that's after they invaded," geopolitical expert Ian Bremmer, the president of Eurasia Group, told Business Insider in an email. "And also, Putin doesn't want to create more antagonism with NATO just as he's making progress with the Europeans - France in particular - in turning back the US-led Western 'isolation' of the Russians."
"There's a very significant economic relationship between the two sides - tourism, trade, and most importantly energy - that neither Putin nor Erdogan want to interfere with," Bremmer added.
According to Reuters, Turkey is (with Egypt) also the largest buyer of Russian wheat and is a significant purchaser of Russian steel semi-finished products. In 2014, 4% of Turkish exports (mainly textiles and food worth about $6 billion) went to Russia.
Tourism is also heavy between the two countries. In 2014, 3.3 million Russian tourists ventured to Turkey - the second-largest number of tourist arrivals after Germany, Reuters reports.
But the energy relationship between the two is indeed the most consequential for both countries.
Turkey strongly depends on Russia for its natural-gas imports. According to The New York Times, Russia provides more than half of Turkey's natural gas.
But Russia also depends on Turkey to transport its natural gas into Europe, especially since its ongoing conflict with Ukraine doesn't show any signs of slowing down.
.jpg)
REUTERS/Ivan Sekretarev/Pool
Russian President Vladimir Putin (R) meets with Turkish President Tayyip Erdogan at the Kremlin in Moscow, Russia, September 23, 2015.
Turkey also has a $20 billion deal with a Russian state-owned firm to build a nuclear power plant in the country.
"Putin's initial reaction - 'a stab in the back by the terrorists' accomplices' - is about as bellicose as could be imagined," Bremmer said. "But Putin is no stranger to harsh rhetoric, and he has broader interests to play for."
Relations between Putin and Erdogan have been deteriorating, especially since the start of Russia's intervention in Syria. Russia has primarily been targeting rebels in Syria unaffiliated with the Islamic State group and supported by Turkey and other countries.
But common interests between the two countries remain, as well as their dependence toward one another.
Erdogan has threatened that Turkey will get its gas from somewhere else and that another country could "come and build" the nuclear plant. And though a different country could indeed come build the plant, getting its gas from somewhere else might prove much more difficult.

Thomson Reuters
Russian President Putin attends meeting with Jordan's King Abdullah at Bocharov Ruchei state residence in Sochi
Although Turkey also receives gas from Iran, Azerbaijan, and Turkmenistan, the country could not receive the amount of gas it obtains from Russia through that current infrastructure.
Russia is also wary of angering its sole current hope to bring its gas more easily to the European Union, especially after the South Stream pipeline through Europe was scrapped.
Turkey is the second biggest exporter of Russian gas after Germany. Considering the state of the Russian economy, it can hardly afford to lose a partner that buys around 30 billion cubic meters of natural gas every year.
Said Bremmer: "I don't think it fundamentally derails the Russia-Turkey relationship, seriously escalates tensions between Russia and NATO, or dramatically changes the dynamics of coalition building around Syria."