An unidentified aerial object entered the airspace of Poland from the direction of the border with Ukraine early on December 29, the Polish Army's Operational Command said. "In the morning, an unidentified aerial object entered the airspace of the Republic of Poland from the side of the border with Ukraine, and from the moment it crossed the border until the signal disappeared, it was observed by the radars of the country's air-defense system," the operational command said on X, formerly Twitter. It said that "In accordance with applicable procedures, the operational commander of the armed forces mobilized the available forces and resources at his disposal." The incident coincided with a massive overnight air attack by Russia on Ukraine.