It's almost a cliche that urban sketchers have to sketch every plane they are on. I've certainly sketched my fair share. Yesterday I flew to Dallas to see the Depeche Mode concert with my sister. This young man was sitting across the aisle from me. Even though I was behind him, he caught me sketching him pretty early on so I showed him and his mom the sketch as it progressed. When it was done he said "I think this is the best painting anyone has ever done of me." About the highest praise I've ever received.