Fourteen European nations have announced they are closing the Baltic Sea to Russia’s "shadow fleet," according to a joint statement released by the British government. Modern shipping depends on satellite navigation not just for positioning but for precise time synchronization vital to systems including the Global Maritime Distress and Safety System, the letter emphasized. It cannot be overcome by traditional navigation techniques when GNSS receivers are baked in to modern ships’ critical systems, including safety systems,” said Captain Ivana-Maria Carionni-Burnett, chair of the Royal Institute of Navigation Maritime Navigation Group. “We stress that the full and consistent implementation of the International Maritime Organization regulations is fundamental to ensuring maritime safety,” the letter stated, citing “the increasing use of shadow fleet vessels to circumvent international sanctions” as a safety threat. The nations called for the development of alternative terrestrial radionavigation systems to substitute for satellite systems during disruption.