ATC does have a big role to play in keeping air travel safe but the first and foremost line of defense are the cockpit crews that fly these planes. We have a instrument on the forward panel that is called TCAS. Traffic Collision Avoidence System. This system displays to the cockpit crew every airplane within a 30 mile radius and can be zoomed down to 3 miles. Display gives altitude information of the target, a climb or descent indictor if the target is climbing or descending more that 500 fpm.
If a target becomes a threat the TCAS will issue a traffic alert and if the target is within 30 seconds of crossing, descending or climbing of our flight path it will issue a descent or climb warning. The crews are mandated to react immediately to resolve the threat and this warning take precedence over ATC clearences. We turn this thing on at the gate before pushback and it's on from taxi out until taxi in at the destination.
This adds a tremdous level of safety. Not saying ATC isn't needed because it surely is but even if there is a moran controller working the crews can see for themselves where every target is. It's always been a pilot's responsibility to "See and Avoid". Would not hesitate to fly my family.
Airline Anon. (retired)
btw all of this depends if the other aircraft has a transponder. And some don't. But in the terminal area of a Class B airspace, a transponder is required.