Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_24399615_4 (airdate VARCHAR, bbc_three_weekly_ranking VARCHAR)
### Question:
What date did the episode air that had n/a for it's bbc three weekly ranking?
### Answer:
SELECT airdate FROM table_24399615_4 WHERE bbc_three_weekly_ranking = "N/A"