After completing the research tests at Holloman Air Force Base, Kranz left McDonnell-Douglas and joined the NASA Space Task Group, then at its Langley Research Center in Virginia.
Upon joining NASA, he was assigned, by flight director Christopher C. Kraft, as a Mission Control procedures officer for the unmanned Mercury-Redstone 1 (MR-1) test (dubbed in Kranz's autobiography as the "Four-Inch Flight", due to its failure to launch).

As Procedures Officer, Kranz was put in charge of integrating Mercury Control with the Launch Control Team at Cape Canaveral, Florida, writing the "Go/NoGo" procedures that allowed missions to continue as planned or be aborted, along with serving as a sort of switchboard operator between the control center at Cape Canaveral and the agency's fourteen tracking stations and two tracking ships (via Teletype) located across the globe.
Kranz performed this role for all unmanned and manned Mercury flights, including the MR-3 and MA-6 flights, which put the first Americans into space and orbit respectively.

After MA-6, he was promoted to Assistant Flight Director for the MA-7 flight of Scott Carpenter in May 1962.
He continued in this role for the remaining two Mercury flights and the first three Gemini flights.
With the upcoming Gemini flights, he was promoted to the Flight Director level and served his first shift, the so-called "operations shift," for the Gemini 4 mission in 1965, the first U.S. EVA and four-day flight.
After Gemini, he served as a Flight Director on odd-numbered Apollo missions, including Apollos 5, 7 and 9, including the first (and only) successful unmanned test of the Lunar Module (Apollo 5).
He was serving as Flight Director for Apollo 11 when the Lunar Module Eagle landed on the Moon on July 20, 1969.
After completing the research tests at Holloman Air Force Base, Kranz left McDonnell-Douglas and joined the NASA Space Task Group, then at its Langley Research Center in Virginia. Upon joining NASA, he was assigned, by flight director Christopher C. Kraft, as a Mission Control procedures officer for the unmanned Mercury-Redstone 1 (MR-1) test (dubbed in Kranz's autobiography as the "Four-Inch Flight", due to its failure to launch).
As Procedures Officer, Kranz was put in charge of integrating Mercury Control with the Launch Control Team at Cape Canaveral, Florida, writing the "Go/NoGo" procedures that allowed missions to continue as planned or be aborted, along with serving as a sort of switchboard operator between the control center at Cape Canaveral and the agency's fourteen tracking stations and two tracking ships (via Teletype) located across the globe. Kranz performed this role for all unmanned and manned Mercury flights, including the MR-3 and MA-6 flights, which put the first Americans into space and orbit respectively.
After MA-6, he was promoted to Assistant Flight Director for the MA-7 flight of Scott Carpenter in May 1962. He continued in this role for the remaining two Mercury flights and the first three Gemini flights. With the upcoming Gemini flights, he was promoted to the Flight Director level and served his first shift, the so-called "operations shift," for the Gemini 4 mission in 1965, the first U.S. EVA and four-day flight. After Gemini, he served as a Flight Director on odd-numbered Apollo missions, including Apollos 5, 7 and 9, including the first (and only) successful unmanned test of the Lunar Module (Apollo 5). He was serving as Flight Director for Apollo 11 when the Lunar Module Eagle landed on the Moon on July 20, 1969.
Gene Kranz