irishpilot1990:
Was the rule not originally brought in following a mid-air collision or a few near miss!?
1. December, 1960: UAL DC-8 plows into TWA Connie over Brooklyn at 5 or 6,000 while blowing a holding fix (one VOR inop) doing barbar pole or there abouts.
This resulted in 250 below 10,000 within 30 miles of the destination airport. No speed restriction on departure once clear of the ATA (now Class D). Also resulted in regulation to report to ATC any en route loss of navigation capability.
2. March, 1967: TWA DC-9-10 going on short range flight (KPIT to either KCMH or KDAY) plows into a Beech Baron at 8,000 while going barbar pole or there abouts.
This resulted in 250 below 10,000 at all times.