Presuming you are in Australia, you have to do the appropriate training to meet CASA reqs.
Most used where I work - Magnetic Particle, Eddy Current and Non Penetrant Dye.
Some useful links below -
Non Destructive Testing - Australian Institute for Non Destructive Testing - Aust Institute of NDT
National Aerospace NDT Board of Australia > Home - Aust Aersospace NDT Board
Its a nice little niche to be in!