Bayan da Armstrong ya zama kwamandan ajiya na Apollo 8, Slayton ya ba shi mukamin kwamandan Apollo 11 a ranar 23 ga Disamba, 1968, kamar yadda Apollo 8 ya kewaye da Moon. A cikin wani taron da ba a ba da sanarwar ba har sai da aka buga tarihin Armstrong a shekara ta 2005, Slayton ya gaya masa cewa kodayake ma'aikatan da aka tsara shi ne kwamandan Armstrong, Lunar Module Pilot Buzz Aldrin, da kuma Kwamandan Kwamandan Kwamandan Kwamandan Michael Collins, ya ba Armstrong damar maye gurbin Aldrin tare da Jim Lovell. Bayan ya yi tunani game da shi har kwana ɗaya, Armstrong ya gaya wa Slayton cewa zai tsaya tare da Aldrin, kamar yadda ba shi da wahala a yi aiki tare da shi kuma ya yi tunanin Lovell ya cancanci nasa umurnin.
14 ga Afrilu, 1969