Sometimes Delta has award sales, and then for a couple of days you can get really good deals, like 30-50K (or less) for an economy R/T across the Atlantic on specific routes. There was a Black Friday / Cyber Monday sale of that ilk for travel through Memorial Day, and then another one that just ended for travel through March. I do not know whether there will be another sale of that type and whether it is for the right destinations or time periods, but keep your eyes open for those. They often are very good deals.