A US-registered Boeing C-17 Globemaster military transport aircraft landed at Moscow’s Vnukovo Airport on Tuesday, prompting questions over the purpose of the flight. The Kremlin said it had no information about the aircraft, while details about its cargo, passengers or reason for arriving in Moscow were not known.

Flight-tracking service Flightradar24 reported that the aircraft, tail number 07-7181, landed in Moscow at about 7 a.m. local time after flying directly from Riga, Latvia. Reuters said it could not independently verify whether the plane was carrying passengers or cargo. Flightradar24 data also showed that the aircraft arrived in Riga from Camp Springs air base near Washington, DC, on August 23.

The report said the most recent direct flight by a US-registered aircraft from Europe to Russia was in January. At that time, US presidential special envoy Steve Witkoff and Jared Kushner travelled to Moscow for peace talks with Russian President Vladimir Putin on the Ukraine war. US-Russia discussions on the war have since effectively stalled, and no official explanation for Tuesday’s flight has been provided.