A pair of Israeli Air Force C-130s that were participating in a flyover to mark the country’s Independence Day made contact in the air and the flight crew were unaware of the incident.
By Oren Rozen (Own work) [CC BY-SA 4.0], via Wikimedia Commons
The mishap was only discovered when ground crew discovered scuff marks on the wings of both aircraft during the post flight inspection.
In other words, they were entirely too close to each other!