Autumn fares NYC to Madrid from just $232
Summer is a great time to pick up some great fares as airlines try to dump their excess inventory. Currently you can find Star Alliance and SkyTeam round-trip fares to Madrid from just $232 from NYC. These fares are not on low cost carrier so you can expect some air mile accruals, bags and meals.
Google Flights show what's available on a month per month basis and pretty much all days are open, excluding the obvious holidays of Thanksgiving and Christmas.
If you need an end of year mileage run these could help you get over the line or a simple trip to do some Christmas shopping in Spain. There are always bargain fares to be found once in Europe so you could also you Madrid as a stopover to visit Paris or anywhere else for that matter.
These will likely not last too long, so have a look and make that booking.