Do airports use private security guards?

From wikipedia: While some countries may have uniform protection at all of their airports, in other countries like the United States, the protection is controlled at the state or local level. The primary personnel will vary and can include:

A police force hired and dedicated to the airport
A branch (substation) of the local police department stationed at the airport
Members of the local police department assigned to the airport as their normal patrol area
Members of a country’s military
Members of a country’s airport protection service
Police dog services for explosive detection, drug detection and other purposes
When additional personnel are required, then several of the groups listed above can be used and as required supplemented by other resources that include:

Officers from the normal agency, but in larger numbers using personnel not normally assigned to the airport
Security guards
Paramilitary forces
Military forces

For more info: http://en.wikipedia.org/wiki/Airport_security