Braving an ominously grey sky, Ine Brants, 33, perches precariously at the top of a stepladder at Liège airport’s perimeter fence. “Ah, the green queen,” she says, raising the long lens of her camera to Challenge Airlines’ green-liveried jumbo jet as it flies into view. “You can get a 747 rush hour here. It has definitely got busier since coronavirus.” Brants’ lens is capturing the Alibaba effect. Quietly over the last three years, Liège,...