This partly gets into the reason why exoatmospheric intercept is preferred. In order to maximize the useful coverage envelope, they need to maximize missile spe

This partly gets into the reason why exoatmospheric intercept is preferred. In order to maximize the useful coverage envelope, they need to maximize missile speed. Unfortunately, there is a speed threshold beyond which endoatmospheric terminal guidance becomes extremely challenging due to limitations imposed by material physics. If your terminal guidance is exoatmospheric, you can mostly avoid those issues. That said, it is clear that the US has been leaning heavily into moving more defense to airborne missile carriers. For example, the SM-6 can now be launched directly from F-18s instead of destroyer VLS cells, which greatly extends the potential range of ballistic missile defense coverage. The B-21 Raider, while it can carry bombs, is essentially an extremely stealthy missile launcher with a very long range and loiter time.