The Baltic country claims Russian jets and vessels neared its borders 13 times last month.
The Baltics have been particularly worried about Russia's annexation of Crimea in 2014.
Donald Trump's recent about-face on NATO didn't influence the long-planned delivery of the U.S.'s most advanced fighter jets.
U.S. tanks are part of a military buildup designed to deter Russian aggression in Eastern Europe.
The incursion lasted around a minute, Estonia's armed forces reported.
Estonia's Ministry of Defence claims Russian jets violated its airspace four times in 2016.
Baltic armed forces are set to practice urban warfare in an artificial town.
Ukraine and Germany join Flaming Thunder for the first time.
Poland's defense minister has confirmed discussions with NATO's Secretary General.
The U.S. presidential hopeful blames Russia's lack of respect for President Barack Obama.
"People need to understand that this is serious business," the U.S. secretary of state said.
Saber Strike 16 will be one of the final tests before a NATO summit in July.
Sergey Naryshkin said the fear of Russia in the Baltics is ingrained.
The program explores a hypothetical hybrid conflict escalating in the Baltics.
The construction of the border fence with Russia will cover an area of around 90km.