For the last few weeks, Simon has been in the UK touring the country with his fellow judges for the Britain's Got Talent auditions.
But this morning, he received a call saying his baby was on its way so dashed straight to the airport to fly back to New York - which takes around seven hours.
Confirming the news, BGT judge Amanda Holden tweeted: "Wishing @simoncowell a safe flight and safe birth."
She added: "Thinking of him and Lauren over the next few hours. Very excited! #simonJr."
Earlier this week, Simon told Reveal that he isn't "nervous" about becoming a father.
He said: "Everyone else around me is more nervous than I am!
"Maybe that will change once it happens, but right now, I'm cool about it."
Celebrities who have announced their pregnancies in 2014:
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