[danbruc]

You can, at the very least, probably aim them a lot better or change the target altogether, for example for misdirection. An ICBM mostly goes up and falls down again on a ballistic trajectory, at least in a first approximation, they can of course correct the trajectory to some extend. On the other hand ICBMs are a lot faster which makes them harder targets for interceptors even if the trajectory is reasonably predictable.

[ethbro]

Fair enough, but what's the use case for this?

I think the reason the project was shelved is that it did provide different capabilities, but none of those capabilities were actually useful in a military context.

That said, after a bit more review, there is one scenario where they would be useful -- launched en masse as a first strike weapon.

While easy to detect at radar range, the smaller boost signature does make launch detection more difficult.

Assuming a launch from the west coast, and design speeds comparable to Pluto (mach 4.2), you'd have about 9 min before they hit Midwest US silos.

Which is one of the other reasons we never developed them. Announcing loudly that you're developing something that's primarily a first strike weapon tends to make the other person jumpy...

[imglorp]

One Cold War era tactic comes to mind, probably void now with modern interception.

A "failsafe point" is where you can stage bombers (or flying bombs in this case) in neutral airspace near your enemy, and have them orbit there for long periods. If things get more tense, you can stage more there without committing to a strike. With tankers, they can park there for days before being swapped out. Then if things turn sour, they're not as far from the target; they can drop to terrain following and go downtown for business. See the awesome Henry Fonda 1964 movie Failsafe for a period story about how talking to your bombers can go wrong.

https://en.wikipedia.org/wiki/Fail-Safe_%28novel%29