克里斯·戈登 /《空军与太空部队杂志》：诺斯罗普·格鲁曼为B-21"突袭者"生产设施动工，空军在投入作战前加速轰炸机测试

原标题 · Chris Gordon / Air & Space Forces Magazine:Northrop Grumman breaks ground on B-21 Raider production facility as Air Force accelerates bomber testing ahead of operational introducti…