The most advanced systems available, even though imperfect, should be put in place now. And replaced by improved systems as they become available. The airline passengers themselves will willingly, and with little economic impact, fund the full deployment. Terrorists will never stop probing to find and exploit the weakest links. That is not a large expenditure for defense, especially considering the difficulty of the problem and the consequences of failure.
Technology is a necessary part of our security chain.
Technology for security must be continuously improved. Improved technologies should be introduced as quickly as they are operational. We cannot let the desire for the ideal drive out the best available. Passengers themselves should pay for the deployment and operating costs of making their flights secure. The government should pay for the research and development.