CREATE TABLE table_204_161 (id DECIMAL, "name" TEXT, "1968 cf\ designator" TEXT, "place of\ manufacture" TEXT, "primary\ role ( s ) " TEXT, "service\ period" TEXT, "#\ used" DECIMAL)

which aircraft has the top number of aircraft in service ?
SELECT "name" FROM table_204_161 ORDER BY "#\nused" DESC LIMIT 1
SELECT "name" FROM "table_204_161" ORDER BY "#\nused" DESC NULLS LAST LIMIT 1