is the fact that commercial aircraft ARE NOT receiving the normal safety inspections that routinely occur when government is functioning normally. These inspectors have been furloughed. Routine maintenance inspections are also not being undertaken right now. Also, there are several levels of redundancy built into the system that are there for the purpose of safety and safety net. As this shutdown has progressed, these layers have disappeared and so has the safety they insure.
As a retired Air Traffic Controller, I can tell you with certainty that these safety concerns are not frivolous matters. For too long, the FAA has failed to advocate strenuously and lobby Congress for financial upgrades to equipment and keep pace with technology, all across this nation. Our airspaces are overcrowded, frighteningly so. Controllers can only do so much with the gear they have. If it breaks down or fails to detect, or when small private planes fail to file flight plans and wander into an aerodrome's airspace (and this happens more often than you know), situations can deteriorate quickly.
Right now, we have ATCs working 10 hour shifts, six days a week to keep pace with shortages. Some are working overtime to fill in the gaps. How many people could keep pace with that kind of a schedule ? The job itself is not inherently stressful - either you have the ability to compartmentalize the requirements or you don't last in the job - but when you start tampering with the structure that supports the system, problems mount exponentially.
Ask yourself, when was the last MAJOR improvement made to Air Traffic Control in this country ? (All I hear is crickets.) When was the last airport built in a major hub ?
Our ATC systems and the people working them are over-taxed. This shutdown has shown us just how dangerously over-burdened they are.