A former NASA engineer claims he saw a nine-foot alien while monitoring a space mission in 1991. Clark McClelland was allegedly part of a team based at the Kennedy Space Center in Cape Canaveral, Florida, when he spotted the extra-terrestrial humanoid. The 'entity', he says, stood on two legs and approached two U.S. astronauts, that he would not name, for one minute and seven seconds in the space shuttle bay. SCROLL DOWN FOR VIDEO . Sighting? Clark McClelland, allegedly pictured during his time with NASA, claims he saw a nine-foot alien . The entity, he claims in a YouTube video, was standing on two legs and interacted with two US astronauts . His story has been hailed by supporters as the most conclusive evidence that intelligent life exists in space. McClelland claims the U.S. government has stripped him of his pension and forced him to live on social security, despite insisting he has served on more than 800 NASA missions. But in a series of YouTube videos, he implores the public to take him seriously. 'I love my planet, I love our human race. I'm trying to serve all of you, if only you will let me,' he tells viewers. Video: Stargate Chronicles . Getting his story out: McClelland has posted pictures from his time with NASA but claims nobody believes him . History: This is allegedly a picture of McClelland (left) with Judy Resnick (right), America's second female astronaut who died in 1986 when her Challenger shuttle broke apart 73 seconds into flight . After more than 800 missions with NASA, he says, he has no pension and lives off social security . McClelland's Twitter profile features a picture billed as his younger self in NASA uniform. In a picture on his website he poses with NASA astronauts by a space shuttle. Another shows a beaming McClelland allegedly stood with Judy Resnick, America's second female astronaut who died in 1986 when her Challenger shuttle broke apart 73 seconds into flight.
Clark McClelland was 'part of more than 800 missions with NASA'
He claims he was watching one 1991 mission when he saw a 9ft entity . The 'humanoid' interacted with two US astronauts for a minute, he says .