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_name_33 ( attendance INTEGER, opponent VARCHAR, date VARCHAR )

### Question ###
What was the attendance on 31 January 2009 when the opponent was Airdrie United?

### Accurate SQL ###

SELECT AVG(attendance) FROM table_name_33 WHERE opponent = "airdrie united" AND date = "31 january 2009"