A totally weird thing I always wonder is how many people are currently 30,000 feet in the air (with me not invited). I've always been sure it's an easy Google search away, but I kind of enjoyed the mystery of it. This interactive map by the Guardian takes away that mystery, and it's incredible.
Guardian made the map in celebration of 100 years of air travel. It shows every commercial flight currently in the air, as well the history of aviation since 1914 and where it'll go from here. According to the narrator, there are 500,000 people in the air right now. So there's my answer. Make sure you click through and play around with the map. It's a blast.