A doctor specialising in colour blindness says there are commercial pilots with the condition working undetected in New Zealand.
Australia allows pilots who have the condition to work on commercial flights, but NZ-registered pilots who fail colour vision testing are not allowed to fly at night or carry fare-paying passengers.
Arthur Pape will tell the Aviation Industry Association's annual conference on Monday that colour blindness does not disadvantage pilots.
He says tests for the condition were easier to pass during the 1970s and 80s, and as pilots don't have to resit them, he's certain there are commercial pilots still flying who slipped through the screening.
The association says Australia allows colour-blind pilots because it has an independent expert panel to consider such conditions.
In New Zealand, it says, that decision belongs to the director of the Civil Aviation Authority, and there's no independent body to resolve differences in expertise.