My father has a career where he works 42 days straight and then has 42 days off. He repairs military helicopters. What other Careers would off a schedule similar to this?

There are oilfield jobs in difficult locations where they will rotate workers, 4 to 8 weeks onsite, then 4 weeks off. Offshore platforms, remote installations, etc, are most common. Certain major construction operations, e.g. construction of a refinery, power plant, etc, are also likely to rotate personnel on such a schedule. Helicopter and charter pilots going to remote areas, e.g. servicing remote construction, oilfield, etc, sites can be on rotations, too. Field engineers, construction site supervisors, heli-pilots – all very technical specializations with a lot of experience & expertise required.

Most jobs offering a rotation schedule like this are remote locations, "hardship posts," military-related, etc. These jobs often don’t last all that long — maybe a year or two at most. These people are often looking for work!