April 2017 we were on a BCN-JFK with 13 other pass rider in J and there were additional empty seats.
We've also waited 4 days to get from AMS to JFK/BOS/DTW/MSP/ATL when weather screwed up the US. Since it was the US side that was screwed up it didn't make sense for us to go somewhere else. We also have decent priority with a 20+ year date.
This April we had a family emergency that required us to get back from AMS immediately. The loads were terrible so we used miles for Award tickets. They're extremely expensive on a same day purchase! One always needs alternate plans and available $ or miles.