As excited fans crowded the performance area and followed along on Twitter, the lack of 1/5 of the band became obvious quite quickly when One Direction showed up for sound check.
While fans speculated that maybe he didn't make his flight to Orlando on time, reports started swirling that Zayn was too sick to perform. The show must go on, however, and the 1D guys are more than capable of picking up Zayn's singing parts (though it's just not the same, honestly).
Today show host Matt Lauer tweeted about the concert, writing: "Where's Zayn? One Direction arrives in Orlando without him. Plenty of questions, but the show goes on Today. #1DTODAY"
He added: "Getting ready to watch @onedirection rehearse for the show. Zayn didn't make the trip to Orlando. We'll ask why before they play. #1DTODAY"
UPDATE: Once the boys took the stage for their pre-show interview, Liam explained that they had just found out this morning about Zayn, that he's sick with a stomach bug.