CREATE TABLE table_72939 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original U.S. air date" TEXT, "Prod. code" FLOAT, "Viewers  ( millions ) " TEXT)

Which US air date had 4.4 million viewers?
SELECT "Original U.S. air date" FROM table_72939 WHERE "Viewers (millions)" = '4.4'
SELECT "Original U.S. air date" FROM "table_72939" WHERE "Viewers (millions)" = '4.4'