A plane carrying Russian President Vladimir Putin to the G20 summit in Germany made a detour of about 500 km (300 miles) to avoid flying over NATO members Poland or the Baltic states, data from a flight tracker showed.
According to the FlightRadar24 website, a Russian government jet flying from Moscow to Hamburg on Thursday deviated from the direct route over Belarus and Poland, which was once a Soviet bloc state but joined the Western military alliance after the fall of communism.
Instead the Ilyushin with the registration number RA-96022 flew over the Baltic Sea, crossing on its way territory of neutral Finland and Sweden before entering the airspace of Denmark and Germany, both NATO members.
Kremlin spokesman Dmitry Peskov declined to comment, saying only that the president's security during trips was paramount.
"The (safety) measures which are taken are expedient measures," he told a conference call with reporters.
Russian television later showed Putin emerging from a plane with same registration in Hamburg as he arrived for the summit, where he had his first meeting with U.S. President Donald Trump on Friday.
Putin has flown over eastern NATO states on a number of recent occasions. It was not clear why this time his jet took a longer route, which also avoided crossing the Baltic states --former Soviet republics which, like Poland, are members of NATO and the European Union.
A NATO F-16 fighter jet buzzed a plane carrying Russian Defence Minister Sergei Shoigu as it flew over the Baltic Sea on June 21, but was seen off by a Russian Sukhoi-27 military jet, Moscow said in an account partly disputed by NATO.
Poland and the Baltic states of Lithuania, Latvia and Estonia have been particularly vocal in their criticism of Moscow since Russia annexed Crimea from Ukraine in 2014.
The region is a flashpoint for tensions between Russia and the Western allies, hosting U.S. and NATO troops, to Moscow's displeasure.
U.S.-led war games were held there this year, rehearsing a scenario in which Russia might try to sever the states from the rest of the Western alliance.
In a speech in Warsaw on Thursday, Trump committed to NATO's guarantee that alliance members will defend each other.
Planes carrying Putin over the past 12 months always took direct routes when flying over EU countries, according to data on FlightRadar24. They did not fly over Ukraine, which has closed off its airspace to flights by Russian airlines.
Putin repeatedly flew over Poland during the period, including for his previous European visit in May, and passed over the Lithuanian capital of Vilnius last October.