What did Neil Armstrong really say when he took his first step on the moon?

Millions on Earth who listened to him on TV or radio heard this: “That’s one small step for man, one giant leap for mankind.”

But after returning from space, Armstrong said that wasn’t what he had planned to say. He said there was a lost word in his famous one-liner from the moon: “That’s one small step for ‘a’ man.” It’s just that people just didn’t hear it.”

During a 30th anniversary gathering in 1999, the Apollo 11 commander acknowledged that he didn’t hear himself say it either when he listened to the transmission from the July 20, 1969, moon landing.

“The ‘a’ was intended,” Armstrong said. “I thought I said it. I can’t hear it when I listen on the radio reception here on Earth, so I’ll be happy if you just put it in parentheses.”

While it seems no one heard the “a,” some research backs Armstrong. In 2006, a computer analysis of sound waves found evidence that Armstrong said what he said he said. NASA has also stood by the moonwalker.

Armstrong, who died in 2012 at age 82, said he came up with the statement himself. In a 2001 NASA oral history, he said NASA discouraged coaching astronauts, a position reflected in a NASA memo. It cited how “the truest emotion … is what the explorer feels within himself.”

“I thought about it after landing,” Armstrong said about his famous line.

“And because we had a lot of other things to do, it was not something that I really concentrated on, but just something that was kind of passing around subliminally or in the background. But it, you know, was a pretty simple statement, talking about stepping off something. Why, it wasn’t a very complex thing. It was what it was.”