The investigation will be interesting
Were they under instructions from an air traffic controller or in free space
If the latter were all of the planes in radio contact
We had a nasty one down here a long while ago and the outcome was all planes in the air at any one time must be bale to communicate with each other & the ground control
This caused a lot of historic planes to be grounded due to lack of a compatiable or functioning radio
A tragedity that was completely avoidable
But like motorcycling, flying is always dangerious