London: One Direction star Niall Horan has slammed a fan on Twitter for taking a photograph of him while he was asleep on a plane. Horan was flying from London to Chicago to see singer Ellie Goulding perform at the Lollapalooza music festival, when he met the fan, who clicked an image of him catching some sleep after he declined a selfie, reports mirror.co.uk. The fan shared the photograph on social media and wrote: "And to sum up the perfect European adventure, I sat directly next to Niall from One Direction for 9 hours on my flight home from London last night. He was sick and asked for no selfies, but here is a pic I snapped when he was sleeping lol he was so friendly." However, the 22-year-old star wasn't amused when he discovered the image on social media and shared the same on Twitter, telling his followers: "I think this s**t is unreal. I mean if you can't sleep on a plane without people taking photos of you, what can you do?"