Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_23508196_5 (type_of_aircraft VARCHAR, number_of_crews VARCHAR)

### Question ###
What is the aircraft for 21 crews?

### Accurate SQL ###

SELECT type_of_aircraft FROM table_23508196_5 WHERE number_of_crews = "21"