I got an SSSS last May on a UA itinerary, YQR-ORD-FLL. It was only my second direct flight from Regina to a US airport (I'd flown two previous flights preclearing in Canada, plus cross by land frequently). I was surprised to get it since I'm NEXUS. I understand that airlines can choose people arbitrarily for SSSS but not sure why I'd be chosen. I booked 3 months in advance and had a return ticket.