It wasn't my idea, and I didn't say it was rational.
From the second reading speeches reported in Hansard:
Mr JOHN COBB (Parkes—Parliamentary Secretary to the Minister for Transport and Regional Services) (1.05 p.m.)
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In summing up, I would like to make mention of the fact that the Aviation Security Amendment Bill 2004 amends the Aviation Transport Security Act 2004 to allow the secretary to declare a person as having adverse security status, with the result that that person's flight crew licence must be cancelled or that, in the case of a new application, their licence would be refused.
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The government considers that it is not unreasonable for pilots to be asked to pay for background checking simply as part of a licensing process. Other aviation industry participants have already paid for background checking.
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Perhaps we should revisit this issue in about 3.5 years…