CREATE TABLE table_2893 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "U.S. viewers  ( million ) " TEXT, "Original air date" TEXT, "Production code" FLOAT)

What was the air date where there were 5.72 million viewers?
SELECT "Original air date" FROM table_2893 WHERE "U.S. viewers (million)" = '5.72'
SELECT "Original air date" FROM "table_2893" WHERE "U.S. viewers (million)" = '5.72'