Editing Apollo 4 (section)

==Mission numbering==
Apollo 4 was the first mission to fly under the official Apollo mission numbering scheme approved by Mueller on April 24, 1967; the planned first crewed flight, in preparation for which three astronauts had died, was retroactively designated Apollo{{nbs}}1 as the widows of the crew members had requested. Although three uncrewed Saturn{{nbs}}IB flights had already occurred, only two had contained an Apollo spacecraft (AS-203 carried only the aerodynamic nose cone). Mueller resumed the numbering sequence at Apollo{{nbs}}4, without designating an Apollo 2 or{{nbs}}3.<ref name="MarAprChron">{{cite book |last1=Ertel |first1=Ivan D. |last2=Newkirk |first2=Roland W. |last3=Brooks |first3=Courtney G. |title=The Apollo Spacecraft: A Chronology |url=http://www.hq.nasa.gov/office/pao/History/SP-4009/contents.htm#Volume%20IV |access-date=March 3, 2011 |volume=IV |year=1969–1978 |publisher=[[NASA]] |location=Washington, D.C. |id=NASA SP-4009 |oclc=23818 |lccn=69060008 |chapter=Part 1 (H): Preparation for Flight, the Accident, and Investigation: March 16 through April 5, 1967 |chapter-url=http://www.hq.nasa.gov/office/pao/History/SP-4009/v4p1h.htm |display-authors=2 |archive-date=February 5, 2008 |archive-url=https://web.archive.org/web/20080205020128/http://www.hq.nasa.gov/office/pao/History/SP-4009/contents.htm#Volume%20IV |url-status=dead }}</ref><ref>{{cite web |url=https://history.nasa.gov/ap11ann/missions.htm |title=Apollo 11 30th Anniversary: Manned Apollo Missions |publisher=NASA History Office |year=1999 |access-date=March 3, 2011 |archive-url=https://web.archive.org/web/20110220232013/https://history.nasa.gov/ap11ann/missions.htm |archive-date=February 20, 2011 |url-status=live}}</ref>