This was reported by AP.
“Though Western surface-to-air missile systems have bolstered Ukraine’s defensives, the visit marked the rare occasion when a U.S. president has traveled to a conflict zone where the U.S. or its allies did not have control over the airspace. The White House would not go into specifics, but national security adviser Jake Sullivan said that it notified Moscow of Biden’s visit to Kyiv shortly before his departure from Washington “for deconfliction purposes” in an effort to avoid any miscalculation that could bring the two nuclear-armed nations into direct conflict,” the publication writes.
The journalists reminded that the US Armed Forces are not present in Ukraine, except for a small detachment of Marines guarding the embassy in Kyiv, which complicated Biden's visit.
According to media reports, while Biden was in Ukraine, American reconnaissance aircraft were monitoring Kyiv from Polish airspace.
According to the publication, Biden spent more than five hours in the Ukrainian capital, meeting with Zelenskyy at the Mariinsky Palace, honoring Ukraine's fallen soldiers, and meeting with US embassy staff in the war-torn country.
A plaque dedicated to Joe Biden was installed on the Alley of Courage in Kyiv as a sign of gratitude for his assistance to Ukraine.