Coconuts, corporate aviation is not a weak link. By what I mean by corporate aviation are aviation departments operated by a corporate company for the use of only their employees and invited passengers.
With small companies as mine all the passengers are known personally by the flight crewmembers and any passengers invited by employees are identified by the employee before they are allowed on board. With larger corporations company issued IDs are used for identification prior to boarding.
The Corporate Aviation Industry has working on security before 9/11 and many companies had security guidelines in place way before anyone had ever heard of TSA.
I was going to add comments about charter and fractional operators, however I will let them respond.
Bottom line is the most secure civilian aviation operators are corporate operators.