Long haul flight outfit and carry-on help?

Flip flops are generally not a good idea for air travel; while an emergency is unlikely, airplanes do have evacuations and crashes, and comfortable closed-in shoes will make you much safer. Long shot, I know, but having been through an emergency evacuation before and seeing the flip-flop people and the high-heel ladies end up barefoot and cutting feet on pavement, I wouldn't ever recommend it.