短語詞組短語official in lower echelon 下級官員officials in lower echelon 下級官員fly in echelon 梯隊飛行squadron in echelon 梯次配置的中隊flying in echelon 成梯隊飛行fly in echelon formation 梯次編隊飛行overall enrichment in echelon 梯次綜郃富集aircraft flying in echelon 成梯隊飛行的飛機 返回 in echelon