At odds with my earlier posts I tend to agree. Our obsession with cleanliness especially with young children completely wipes out our immune system. Chickenpox is a difficult one. Proving whether somebody is infectious must be difficult. You are taking the word of the individual of when the spots came out. The bottom line is that the airlines have rules, and I would think the doctor involved is taking a huge risk advising a family to ignore them. Even recently I have been told by a doctor that he cannot sign a fit to fly cetificate for my wife to fly at 29 weeks pregnant, because the BMA advise them of liability problems.