General Discussion

They were both flying VFR (not using instruments). It was very sunny. One of the planes had been delayed by 13 minutes and didn't anticipate it. They were both cleared to land at two different airports. There is no indication that the plane that was headed to Oshkosh spoke with ATC in Appleton. The plane headed to Appleton was delayed by 13 minutes and was only five miles or so from their destination.

1972 Lake Winnebago mid-air collision

The National Transportation Safety Board noted that the North Central crew would have had to look toward the sun to see the approaching Air Wisconsin plane[2][6] and concluded that they took no evasive action.[

The report also noted that the decision by both flight crews to fly under VFR rather than IFR and the fact that neither captain requested in-flight advisories deprived both aircraft of air traffic control support, and that such support to even one of the aircraft would have ensured sufficient separation to avoid a collision.[7]

The NTSB recommended that the Federal Aviation Administration create a standardized method for training and grading flight crews in visual search techniques and time-sharing between instrument checks and visual searches, and that the FAA expedite the development of anticollision systems.[11]
https://en.wikipedia.org/wiki/1972_Lake_Winnebago_mid-air_collision

____

Gosh this seems so ancient. Commercial carriers flying VFR just because the weather was nice? They don't do this anymore. Flying has gotten much safer.