On what air date were there 2.15 million u.s. viewers?
CREATE TABLE table_22380270_1 (
    original_air_date VARCHAR,
    us_viewers__millions_ VARCHAR
)
SELECT original_air_date FROM table_22380270_1 WHERE us_viewers__millions_ = "2.15"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: On what air date were there 2.15 million u.s. viewers? ### Input: CREATE TABLE table_22380270_1 (
    original_air_date VARCHAR,
    us_viewers__millions_ VARCHAR
) ### Response: SELECT original_air_date FROM table_22380270_1 WHERE us_viewers__millions_ = "2.15"