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_23508196_5 (type_of_aircraft VARCHAR, number_of_crews VARCHAR)
### Question:
What is the aircraft for 21 crews?
### Answer:
SELECT type_of_aircraft FROM table_23508196_5 WHERE number_of_crews = "21"