Russia pushed a new air-safety initiative for the Baltic Sea in a meeting with North Atlantic Treaty Organization ambassadors Wednesday as it continued to criticize the Western alliance for a planned buildup in the region.

Moscow’s air-safety proposal would require all planes flying in the Baltic Sea region to operate with their transponders turned on, Russian officials said. Transponders help civil aviation authorities track and identify planes. U.S., NATO and European Union officials in the past have criticized the Russian...