I'm not so sure. That a place like London can support all the high-yield traffic an airline can throw at it does not imply that it is more profitable for any individual airline than a more broadly spread route network. In other words, that it is easy to sell out a J cabin to Heathrow does not mean that the one airline which chooses to serve ATL-CPT won't be able to also fill their J cabin, perhaps at a higher profitability. Yes, there is more total money in the major markets, but there are also more players dividing up the pie.

And even if we assume that major markets are the most important, what does it mean for such a strategy that UA does not have the same international presence in the single largest market in the US that DL has? Flying IAD-FRA is great, since FRA is a big market, but flying NYC-BRU is also pretty great, since NYC is a pretty big market too.

Personally, I think DL needs to merge to achieve the kind of scale to really compete with the big foreign carriers. But, if that isn't going to happen, I think that DL has made some very smart moves recently in choosing a route network that is well-matched to their fleet, their geographic strongholds, and the competitive landscape. I think the 767 is a good plane to serve the US-Europe market. It allows DL to compete to a lot of different destinations, minimizing their exposure to competition from the likes of AF, LH, and BA, which will likely continue to dominate the markets to their European strongholds. And the new 777s are the perfect plane to compliment that strategy, allowing DL to provide enough service to enough far-flung destinations to keep their key customers happy.

I'm not guaranteeing that DL will come out ahead but, on paper, their strategy makes as much (or more) sense as any of the other US carriers.