I would emphasize that point. When we look to the future, we have to look at what possible aircraft we'd be required to fly against. It's not just aircraft. It's also ground-based, surface-to-air missile systems. It's a whole package of military capabilities that are emergent or could be in the future that we would have to contend with.
The other part of that threat formula of capability plus intent is often the most difficult to forecast with any kind of accuracy, so we look at countries like China and Russia, which have very high-end military capabilities, and the potential for some of those capabilities to proliferate to different areas of the world. If we're going to operate in the future and in the time frame that we're talking about for something like a fighter aircraft that's going to operate for many decades, then we need to make sure we're getting something that's going to be able to operate against those kinds of adversaries.
It is a very difficult question.