Darren Harrison spoke to Savannah Guthrie on "Today" ... and explained with all the buttons and gadgets on the control panel, it all came down to common sense.

The emergency was even more harrowing than first reported. The 39-year-old said after the pilot became incapacitated, the Cessna began to nose-dive at a high rate of speed.

Harrison was cool as a cucumber, saying, “I knew if I didn’t react, then we would die."

As he put it ... “I was pretty calm and collected the whole time because I knew it was a life or death situation. Either you do what you have to do to control the situation or you’re gonna die.”

Harrison, who works at a flooring company, said his wife, Britney, who was 7-months pregnant with their unborn daughter, was his inspiration. He also said there was an element of divine intervention, telling Guthrie “the hand of God was on that plane."

As he said, “I was climbing to the front and that plane was in a dive. I was just looking going, ‘I can’t die today. Britney’s pregnant, I’ve got a baby on the way — not today. Today’s not my day."

As we reported, Harrison contacted the tower operator who help guide him down to the runway, where he made a perfect landing ... just incredible.