North Korean leader Kim Jong Un peered into the cockpit of Russia’s most advanced fighter jet as he toured an aircraft factory on Friday on an extended trip that has raised concerns about banned weapons transfer deals between the two countries.

Since entering Russia aboard his armored train on Tuesday, Kim has met President Vladimir Putin and visited weapons and technology sites, underscoring deepening ties between the two nations locked in separate confrontations with the West. Foreign governments and experts speculate Kim will likely supply ammunition to Russia for its war efforts in Ukraine in exchange for receiving advanced weapons or technology from Russia.