Would ash effect good old fashioned liquid-cooled piston engines (Merlin/DB601/Allison/...) equipped with filters? Would be ironic to be thrown back into the propeller age... but according to the scientists, the eruption of ash has stopped, which makes fears come to life that the neighbouring larger volcano Katla may awaken - and if that happens, ash could be spewn out for months in much larger proportions than so far...
Sometimes, I can't help but to be amazed at how good old Mother Nature forces a slower pace of life on us. The alternatives to air transportation would result in trips that by plane take only hours, to be traversed in days or even weeks...
Edit: Hmmm, instead of Helos, GrViper, how about Blimps? Sound more practical I think, besides more economical, given the amounts of people and cargo to be transported...