Airliners nearly collided in midair east of Hawaii

Wow. That was very close to disaster. Good thing that both flight crews responded safely.

IMO the system should warn them sooner than 12.9km

The old collision avoidance system worked but only just. with a closing speed of 1200MPH, it has to react immediately. If both crews climb, or if they both dive at the same time, it's game over for both of them.

Old? The Traffic Alert and Collision Avoidance System is the last line of defense in avoiding a collision. The air traffic controllers cleared each of them for altitude and course which put them in that position. They are allowed a buffer of five miles laterally and 1,000 feet vertically. Someone either put one of them at the wrong altitude or one was set at the wrong altitude. Usually opposing flight directions are given either odd or even flight altitudes to give them the minimum 1,000'.

Old? The Traffic Alert and Collision Avoidance System is the last line of defense in avoiding a collision.

It's been around for decades, has it not? I doubt that it gets used very often (I would hope not, anyway).

The system name has been around for years but they have been improved as technology advances. It's used every second of every flight, but is only acted upon when the warning goes off. It could be quite common for the indicator to go off and measures taken to avoid a collision. In this case passengers were physically made aware and then used social media to broadcast it.

Will all the planes up there nowadays I have a feeling this happens far more often than is reported.

If you fly North-South along the Eastern Seaboard of the U.S., you see planes go whizzing by in the other direction, all of the time. It's pretty startling, both the proximity to the other planes and the dramatic closing speed. We have a lot of faith that the system is working properly.

Yup.