A U.S. military transport plane used by the United States Air Force flew from Latvia to Moscow's Vnukovo airport early on Aug. 25, data from Flightradar24 showed.
The plane appeared to have travelled to Latvia from Joint Base Andrews, a U.S. military facility close to Washington DC, the data showed.
The data did not show who was onboard the plane — a large, Boeing C-17 Globemaster III — or why it was travelling to Russia.
Kremlin spokesman Dmitry Peskov declined to comment when asked about the flight, saying he did "not have such information".
The U.S. administration has made no public comment on the matter.
U.S. officials have visited Russia several times in recent years, although it was not clear whether civilian or military officials were onboard.
Flightradar24, a website founded by two Swedish aviation enthusiasts, uses a crowd-sourced system of aircraft receivers to map out the location and flight paths of aircraft across the world.
AFP was not able to immediately verify the data.
