Sungod17 saidI could see it being feasible for moving civilian cargo, depending on the economics. But wouldn't a big, fat, slow balloon be pathetically easy to shoot down in a military role? Back when the Navy was using them in the early days-primarily for reconnaissance- the missile technology was not as much of a factor.
The surface to air missile threat is definitely a concern; however, there a quite a few ways in which it is mitigated in theatre:
1) Man portable surface to air missiles (MANPADs) typically have a range of around 5 km. The better MANPADs are made by western countries, especially our own Stinger, so the majority of whatever the Taliban might be armed with are more than likely poorer performing, older Soviet bloc weapons, such as the SA-7. During the campaign, 70% of the time a Stinger was fired, a Soviet aircraft went down; the SA-7 had an approximately 30% success rate.
While we did fund and arm the mujahideen's insurgency to the Soviet invasion of the 1980's with billions of dollars of weaponry, the guidance sysetms for all of the MANPADs we provided have degraded beyond use. Guidance and target acquisition systems naturally deteriorate over time. Every 5-10 years they need to be maintenanced in order for the missile to be able to lock on to a target and guide itself towards it. It's been over 20 years since the last shipment of US funded weaponry to the Taliban, so all of those MANPADs which were delivered have either already been used or are degraded beyond use. Additionally, for a missile to have even that long of a life before needing to be maintained, it would need to be stored in a cliate controlled environment. The caves of southern and eastern Afghanistan are hardly an ideal location.
Soviet bloc nations and their black market arms dealers would have little to no interest in smuggling weapons to the Taliban. The Taliban leadership are the same people who over 20 years ago killed around 28,000 Russian soldiers. The black market is run by a lot of ex-military guys who after the collapse of the Soviet Union were out of a job. All of them undoubtedly lost friends to the mujahideen.
2) Surface to Air Missile sites (SAMs) are much larger missiles that are typically vehicle mounted. These are non-existent in Afghanistan for a multitude of reasons. They are too technical for the Taliban to operate, they are not mobile enough to be used in an insurgency, and they are very expensive.
3) Heavy machine guns typically have a range of around 1-2km. The airfields would be well beyond their effective range, provided the military bases in Afghanistan have an effective security posture and a manned perimeter (they do). Even if this weren't the case, the airships would just land at night.