I always wonder why companies decide to fly such old aircraft from the perspective of cost. Romantic reasons, I understand, I used to fly on them regularly with MidPac Air
N109MP Mid Pacific Air | Flickr - Photo Sharing! back in the day and the experience was always pleasant. However, the difficulties as ably explained by cvg2iln whilst operating them years ago spell out the challenges. I can't believe that it would make financial sense, but would be happy to be proved wrong.
SHJ