The Syco boss invited sound recordist John Hagenstede to join him on his private jet after discovering that his girlfriend Lisa had gone into labour at the end of auditions in Edinburgh yesterday (February 11).
The 44-year-old accompanied Cowell, Alesha Dixon and David Walliams on the journey to Luton Airport, before rushing over to Surrey and joining his partner.
"Lisa wasn't due for another nine days, so I was shocked to get the call and desperately wanted to get back to Surrey to be with her," Hagenstede said.
"We looked up every possible option of getting me home and I was devastated when I realised the only option was waiting and getting a flight in the morning. I knew I would miss the birth of my first child.
"Simon, David and Alesha were so brilliant. They knew how important it was to me and not only did they let me share their private jet, they also gave me drinks on the flight, relaxed me and were generally lovely and supportive.
"As I left Simon, David and Alesha wished me luck and offered their congratulations."
Hagenstede arrived just in time to witness the birth of his son, who the couple named Jude.
"I got there with just moments to spare," he said. "If I'd have got there ten minutes later, I'd have missed the birth of my son.
"I'm so grateful to Simon. Without him there was no way I'd have been there for that precious moment."
This weekend's Edinburgh auditions saw Amanda Holden return to the panel for the first time since giving birth to daughter Hollie on January 23.