The Avengers Assemble movie has been out for a while so I think this doesn’t really count as a spoiler, anyway it features a flying aircraft carrier:
Leaving aside the implausibility of the technology involved would there really be any particular military or political benefit from building one? From what I can see:
Benefits:
Faster movement and not restricted to sea-lanes etc can operate over land
Intimidation factor
It looks cool
Drawbacks:
Aircraft carriers don’t operate in isolation, you would need an entire flying carrier battle-group, which would really need magical future technology to keep operating
Greater vulnerability, its hard to sink an aircraft carrier, I imagine it would be markedly easier to shoot one down
May not be a good thing to be below said shot-down aircraft carrier
The driving idea is that for any given level of tech, big and small machines have differing tradeoffs. A way to get the best of both worlds is to combine the two together as co-operating but separable units.
The problems are pretty obvious. In each real world case the real show-stopper has been taking off and landing reliably from another airborne vehicle. If we could ever have mastered that we might have gone somewhere with the concept. Instead we pushed the state of the art in other directions. As explained in detail in that article.
Another thing:
If we had the tech to build the *Avengers *carrier, the fighters would be utterly different from the conventional-looking ones shown. Because they could use some of the same magic tech to themselves carry insane weights of armament for long durations and great distances. Thereby mostly obviating the thing the aerial carrier provides.
If we count the F-22 or F-35 possibly deploying missile-launching UAVs, it already exists.
Easier to detect/track/engage the carrier. One of the main advantages of the aircraft carrier is that it can use its aircraft to indirectly recce/shoot/EW beyond the radar horizon while remaining below it.
So, you’d have to have it flying at low altitude. I suppose a large ground effect vehicle might, perhaps, be utilized as a light aircraft carrier while only having to rely on distant and very expensive tech rather than unobtainium.
Still though, better to have many carriers stationed in many places than rely on deploying them quickly by air. If you want to use aircraft far away and faster and you don’t have nearby bases or sea-based carriers, you can use in-flight refueling.
Look up the Lockheed CL-1201, it was a design study about creating a giant flying wing aircraft that was nuclear powered so it could fly for 40 days continuously, carried 22 fighter aircraft under its wing for protection, and could only land and take-off from oceans because there was no runway wide enough to allow it to land.
There were two types envisioned, an offensive aircraft carrier with the aforementioned fighters or a straight logistics version which could carry thousands of troops and equipment and could refuel five aircraft at once.
Aircraft have the benefits of being able to attack inland, move quickly, and quickly intercept incoming hostiles, but have the drawback of short dwell times: You can’t simply park an airplane in one place for very long before it has to go back to some sort of base to refuel.
Ships have the benefit of long dwell times, but aren’t nearly as fast as aircraft, and are restricted to the seas.
An aircraft carrier is one way of combining the benefits of both: You can steam out to your trouble spot in the carrier, the planes can take off from it, and land back on it when needed.
But if you had the technology to build a flying aircraft carrier, you could use that tech to build a single vehicle that had all of the benefits of both, without needing one vehicle to land on another.
To be fair, while most of the fighters used seemed to be the same as what the current Navy and Air Force use, they also had a smaller number of quinjets, which seemed to have a much greater weight-to-size ratio, and could easily take off and land from a farmer’s field. That looks like it might have been similar tech.
The amount of energy required to keep a 110,000 ton supercarrier in the air, not to mention the sheer volume of air needed to be moved through four large fans, place this rather permanently in the realm of science fiction.
Even if you said it only weighed, say, 30,000 tons, it’d be out of the question.
One of the things that bothered me about the Avengers carrier was the distinct lack of short ranged defensive or offensive weaponry. Other than Fury stepping out on the deck with a shoulder fired missile, they had no way to stop a rogue jet from taking off or Loki’s helicopter from leaving? Now, they may be depending on the sheer size of it to render most anti-aircraft weapons ineffective (an AIM-9 for example is going to do much), but those engines were so vulnerable that a squadron of enemy fighters could focus fire on them and take the whole thing down.
For that matter, I couldn’t understand why Ultron didn’t just suicide 20-30 of his units into those engines.
If you could magically overcome the technological limitations, there are many good reasons to want a flying aircraft carrier. (1) You have a mobile airport and all the advantages that come with it, (2) you eliminate or simplify the logistical problem of mid-air refueling during a mission, (3) reduce wear and tear on aircraft and personnel, (4) avoid the limitations of dry land (there’s a reason we invest huge amounts of capital in building canals!), (5) it might be faster than a naval fleet and (6) it might be able to fly over severe weather. The naval aircraft carrier is a critical backbone to force projection and I can entirely understand why a flying version would be desirable.
But as others have pointed out, the real life technical limitations are insurmountable. Between the fuel, weight, maintenance, and all the other nonsense that comic books just ignore, it would be far too resource intensive to attempt. The other big problem is that they crash. A lot. It has become a very consistent trope that anytime the writer wants to establish how powerful the villain is or how much danger the characters are in, they crash one or more helicarriers. It might be dramatic if it happened once or twice, and it was a major part of the plot. But SHIELD Agents in general are the red-shirted ensigns of the comic book world and helicarriers crash with annoying regularity, to the point that I can’t figure out why anyone is dumb enough to bother trying.
