These routes strike me as the most business centric O&D routes they could experiment with. Perhaps they are choosing them to prove that E fares allow them to retain high-fare business travelers while discounting extra inventory.

Currently, the difference is a minimal $20/each way for SEA-LHR. If and only if that continues to hold, this is mostly just a $40 price hike for these markets. But it's inevitable that they'll eventually offer sale fares only in E class, and when that happens and the price difference becomes more dramatic, it could spell the end of Delta as an attractive and affordable option for international leisure travel.

One thing's clear: between Comfort+ changes and now this, iDelta is no longer the airline to select if you care about where you sit on the airplane and expect your elite status to give you a choice of seats.