The missile-defense system work by using SAMs (Surface-to-Air Missiles). Having a nuke counter an ICBM will lead to far worse fallout. While you're correct, the planes don't want to be in that crossfire, the missile targeting system would more than easily account for civilian aircraft and avoid them.
SAMs aren't an alternative to nukes because SAMs can be nukes. The (retired) US Nike-Hercules (intended for anti-bomber) and Nike-Zeus (anti-warhead and, at least in testing, also anti-satellite for Zeus B) are examples.
(Note, if you live in the Bay Area there are a whole bunch of decommissioned bases for these missiles around.)
> Having a nuke counter an ICBM will lead to far worse fallout.
Nuclear airbursts that aren't in close proximity to the ground relative to yield have essentially zero fallout (fallout is basically irradiated debris from the ground kicked into the air by the explosion.) It may or may not increase the amount of flash radiation, but that's a shorter-term, smaller area problem. But the US doesn't (at least officially, and I doubt this could be effectively concealed) rely on nuclear air-to-surface defenses any more.
But any nuclear attack has an EMP risk, and I don't think a plane is where you want to be during an EMP. Plus, people on the ground when a threat is confirmed have a better chance of being able to follow an order to shelter than those in the air.
From a civil defense perspective, “ground the planes in the potential target area immediately and unconditionally on launch warning” makes a whole lot of sense.
https://en.wikipedia.org/wiki/AIR-2_Genie
https://en.wikipedia.org/wiki/Nike_Zeus
https://en.wikipedia.org/wiki/Sprint_(missile)
https://en.wikipedia.org/wiki/A-135_anti-ballistic_missile_s... (currently active!)
Fallout is better than a city blowing up - we used to test nukes in the atmosphere, and while we've recognized that's not great, the calculus changes a bit with a nuke coming to blow up NYC or LA. You're right that we don't have nuclear-tipped anti-ballistic missiles currently, opting for more accurate conventional ABMs, but that's more about the US and Russia trying to reduce their nuclear arsenals.
ICBMs travel in excess of Mach 10, and typical SAMs are Mach 1 to Mach 5.
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Instead of using a small explosive to bring down an enemy nuke, surely there's an idea to use a bigger counter-nuke? Sure, there's going to be a ton of fallout, but that's still better than losing the entirety of San Francisco.
Its a lot easier to hit an enemy missile with a big-bomb, rather than using a little bomb. IE: load those SAMs with nukes and have at it. Even if you're slower, you got the strength and blast-radius of a nuke and have a better chance of bringing down the enemy ICBM.
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I don't think its an issue of "airplanes would be hit by a SAM". I think it's seriously the risk of airplanes literally getting caught in the blasts (that were aimed at the enemy missile).
Yes; Russia protects Moscow with such a system.
https://en.wikipedia.org/wiki/A-135_anti-ballistic_missile_s...
Army - Patriot
Army / Missile Defense Agency - THAAD
Army / Air Force / Missile Defense Agency - Ground-Based Midcourse Defense w/ GMI
Navy - Aegis w/ SM-3 (also, Aegis Ashore)
[1] - https://en.wikipedia.org/wiki/RIM-161_Standard_Missile_3
The most interesting is Terminal High Altitude Area Defense (THAAD)
https://en.wikipedia.org/wiki/Terminal_High_Altitude_Area_De...
Basically you launch a missile that intercepts a high altitude missile and launch an object at it in a 'hit-to-kill'. It's been fairly successful in testing according to the link.
Do it high enough up and it's got similar fallout to the atmospheric tests we used to do. Not great, but better than millions dead on the ground.
High-altitude airbursts produce essentially no fallout; fallout is from tossing irradiated ground debris into the air from a ground burst or near-ground burst. Other than the missile itself and it's target, there's nothing for a high-altitude airburst to make fallout from.
> We don't have them currently, but both the US and Russia have tinkered with the concept.
“Widely deployed”, not “tinkered with”.