Though I've never flown the Atlantic via Greenland, I know it's common for ferry pilots to wear a survival suit on the flight over water. There's just no way you'd be able to don a survival suit in the cramped quarters of an airplane cockpit. They usually wear them half on, with their legs in the lower portion, but not their arms in the upper part. I think wearing a fully donned survival suit in flight would be way too hot for comfort.