During their live interview with The Today Show, Zayn's bandmate Liam Payne revealed that Zayn had come down with a nasty cold and was unable to fly.
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"He's just at home, he needs to rest", Liam told host Matt Lauer.
"Zayn was taken ill after recording the Band Aid single at the weekend and was unfortunately not well enough to fly to the USA yesterday. He will join the band for promotion for the new album as soon as he possibly can", a representative for the band told the Daily Mail.
The One Direction boys arrived to the interview by speedboat, waving to the reported 15,000 fans who had gathered from the early hours of the morning to catch a glimpse of their favourites.
Held at Universal Citywalk in Orlando, the four lads were promoting their new album Four, which was released on Monday.
On Saturday the boys all arrived at a music studio in London to help record the new Band Aid 30 single, Do They Know It's Christmas?, for the Ebola crisis. It came days after they met the Duke and Duchess of Cambridge at the Royal Variety Performance, where Harry Styles took the moment to congratulate the Duchess on her pregnancy.
Speaking afterwards, Harry told reporters: "I said congratulations on the bump... she didn't look bumpy."