Timing seems right...
By May, 1961, only five months after the mid-air, the FAA was in the process of changing some aspects of Part 60 (Air Traffic Rules) of the Civil Air Regulations. One change had to do with amending the "Coded Radar Beacon Transponder Requirement in Positive Air Traffic Control Areas and Jet Advisory Areas," and another related to "Regulation of Aircraft Speed."
You may be interested to note that the FAA proposal (and subsequent rule) was for arriving traffic below 14,500, rather than 10,000. As proposed:
60.27 Aircraft Speed. Below 14,500 feet mean sea level and within 50 nautical miles of the airport of destination, no person shall operate an arriving aircraft at an indicated air speed in excess of 250 knots (288 mph) unless the operating limitations or military normal operating procedures require a greater minimum air speed, in which case the aircraft shall not be flown in excess of such speed.
There was a lot of comment on the proposed rule, including data arguing that it would cost airlines as much as $15,000,000 per year to comply.
The final rule adopted some of the arguments raised in the public comment period, and read as follows:
60.27 Aircraft speed.
A person shall not operate an arriving aircraft at an indicated airspeed in excess of 250 knots (288 m.p.h.) during flight below 10,000 feet mean sea level within 30 nautical miles of an airport where a landing is intended or where a simulated approach will be conducted unless the operating limitations or military normal operating procedures require a greater airspeed, in which case the aircraft shall not be flown in excess of such speed.
This amendment shall become effective on December 19, 1961.
(Sec. 307 of the Federal Aviation Act of 1958; 72 Stat. 749; 49 U.S.C. 1348)
Issued in Washington, D.C., on November 13, 1961.
Note that Part 60 did not address speed below 10,000 prior to this date, and, as I said, even with this change the limit only applied to arriving aircraft.
Interestingly, some commentors on the proposed rule argued that it would make ATC more difficult rather than easier...
I'd be happy to provide the full text of (what would now be called ) the Notice of Proposed Rulemaking as well as the announcement which went along with the new rule itself to anyone who would like to see it.
Dave
Edited to make note of the fact that in the 1960 mid-air, a minute before the collision United was out of 6,000 in the descent at 356 knots indicated...