15,000 feet is too low.
If it's 15,000 feet above sea level then it's well within range of AAA in most mountanous terrain like Afghanistan. The ancient Russian S-60 57mm AAA was used with great effect against fast jets in Vietnam in the 1000-5000 feet arena, often scored hits as high as 8,000 feet, and there are plenty of them in Afghanistan left by the Russians. A 60-knot blimp would be regarded as target practice! Then there are the large number of Blowpipe, SA-7/SA-14 and Stinger SAMs which should be quite capable of hitting the 15,000 feet ceiling when fired from a 12,000 foot mountaintop, and of which are easier to hide than the S-60. All three have been used in Afghanistan. Even anti-tank missiles like the Pakistani Baktar-Shikan would be effective. It simply becomes a matter of how many and how big holes do you need to punch through it to make it crash.
Whilst such blimps might be of value in very low intensity conflicts such as policing over downtown Bahgdad, to survive over more hostile territory the platform needs to be small, fast and discrete, or 30,000+ feet up and able to hold position in the jetstream, let alone ordinary weather. The loss of the mentioned USS Macon shows how limited airships really are.