"Cost of what's required"
The director of ports insists plans to expand and improve the airport security area are necessary and proportionate.
The matter was raised as Ann Reynolds appeared before a Tynwald select committee with the infrastructure minister and his chief executive at the end of last week.
Since summer last year, there have been times when there have been substantial queues at Ronaldsway.
Passenger watchdog TravelWatch has branded the work unnecessary, saying spending £300,000 on the work is simply 'throwing money at the problem'.
Ms Reynolds says that is the cost of what is required:
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