CREATE TABLE table_17467447_1 (original_airdate VARCHAR, us_viewers__million_ VARCHAR)

What is the air date when the U.S. viewers was 5.50 million?
SELECT original_airdate FROM table_17467447_1 WHERE us_viewers__million_ = "5.50"
SELECT "original_airdate" FROM "table_17467447_1" WHERE "5.50" = "us_viewers__million_"