[July 21st, 1921] United States Army Air Service Martin NBS-1 bombers sink the decommissioned German battleship "Ostfriesland" in the Atlantic Ocean off the Virginia Capes after Brigadier General Billy Mitchell argued for bombing trials to show the power of aircraft to sink major warships.
from /r/100yearsago
[1921年7月21日]美国陆军航空兵马丁NBS-1轰炸机在弗吉尼亚海角附近的大西洋上击沉了退役的德国战舰 "奥斯特弗里斯兰 "号，此前比利-米切尔准将主张进行轰炸试验以显示飞机击沉主要战舰的能力。