CNN joined NATO on its Airborne Warning and Control System plane, which is used on the Ukrainian-Polish border to collect intelligence. The Russians know the planes are there and try to jam their radar, NATO's technical director told CNN.
NATO mission's technical director told the outlet the "vast majority" of Russian jets have been found coming to Ukraine from Belarus, a neighboring country and ally to Russian President Vladimir Putin.
A U.S. defense official said this week Russia is launching air operations from Belarus, the Black Sea, Russia and Ukraine.
The NATO members on the plane say it is hard to tell if Belarus has any of its own troops participating in the war as Russia, Belarus and Ukraine all use similar fighter jets.
NATO tactical director Denis Guillaume said Thursday that a dozen Russian jets were idling in Belarus. When asked by CNN if NATO is sharing this intelligence with Ukraine, he declined to answer.
"I cannot answer that question," Guillaume said. The technical director told the outlet, "The only thing I can tell you right now is that we, as NATO allies, are sharing the data with NATO countries."
However, the technical director said the NATO countries can do with the intelligence what they want. Although it isn't clear what information the U.S. is sending Ukraine, it is known the country has been sharing intelligence to help Ukraine's fight against Russia.
NATO countries have begun sanctioning Belarus's banks and individual citizens in response to the nation letting Russia the country in its invasion of Ukraine. Before the invasion, Belarus let Russia build up thousands of troops on its borders to eventually enter Ukraine.
Ukrainian officials have called for a no-fly zone in Ukraine to counter Russia's air operations, but the request has been denied by NATO.