On Oct. 20, the National Nuclear Security Administration (NNSA) and United States Air Force conducted the third development test of an unarmed B61-12 nuclear gravity bomb at Nevada's Tonopah Test Range. As you can see below, the test drop was a success. Not bad for a bomb with no propulsion system.
The B61-12 is currently undergoing an $8 billion refurbishment program intended to keep the oldest nukes in the US arsenal active and relevant until 2040. What were formerly the last remnants of "dumb" nuclear bombs—that is, completely unguided ordinance dropped from airplanes—have now been outfitted with new tail sections featuring a GPS-enabled inertial navigation system. The result isn't exactly a cruise missile, but it does have the targeting ability required of a tactical nuclear weapon.
Eventually, 400 to 500 B61 bombs will be refurbished at Sandia National Laboratories to meet the new specifications. The Bulletin of the Atomic Scientists has estimated that around 1,200 B61s remain operational in total.
The B61s have a helpful capability known as variable yield. That is, the operator of any particular bomb has the capability of "dialing in" a yield of anywhere from .3 to 340 kilotons. For tactical uses, where nukes are used on relatively small scales—against an airfield or advancing infantry unit, for example—this is a useful capability. So, even as the US and Soviet Union worked to fulfill the promises of Mutually Assured Destruction with silos and submarines full of world-ending ICBMs, they kept the dream alive of "reasonable" nuclear warfare via these small-scale vestiges of the Castle Bravo H-bomb which could be delivered old-school from airplanes.
There's another, bleaker reason to keep relatively dumb nuclear weapons around, as James Drew explains at War Is Boring: "The equipment will work even if America's navigation satellites are shot to pieces—a likely scenario during a nuclear war—and is hardened to survive the electromagnetic pulse generated by a high-altitude nuclear explosion."
So, rest easy. Even when you and everything you know and care about have been vaporized, the US will still be able to keep the party going with gravity bombs. Phew.