Forgive my bluntness, but ... in my opinion, your question is flawed.

We can never "achieve secure flying". Security is not a "yes/no" characteristic. We can't say "this flight is secure" or "this flight is not secure". It's all a matter of degrees. Some flights are more secure than others. Flights today might (or might not be) more secure than flights ten years ago. And so on.

The question, really, should be this. What security procedures are worth implementing? For each procedure one might consider implementing, there are benefits: the increased safety provided by the procedure. There are also costs: the time required to perform the procedure, the money required to pay for the procedure (both in people and equipment), the loss of liberty inherent in the procedure, and so on. For each procedure, we can discuss whether the costs outweigh the benefits.

After all, we could always implement security procedures like "Con-Air" uses for all commercial flights. It would certainly be much more secure than current commercial air travel. But very few people would choose to fly commercially under those conditions.

On the other hand, we could go back to a wild-West "buyer beware" sort of security, where we don't do anything, and tell passengers that the airlines don't make any guarantees regarding safety. It'd be cheap. But, again, very few people would choose to fly commercially in that sort of environment.

The level of security we want lies somewhere between those two extremes. Where, exactly, is that? Well ... that's what we like to fight about discuss in these forums.