Pregnant wife will be traveling from michigan to california by plane ( 4hours ) she will be 29 weeks, returning home by plane when she is 32 weeks. can she travel. is it safe. possibility of birth on plane?

Sure, but it...: Won't happen, because a woman with normal self-awareness is not going to hop onto a domestic flight while contracting. That means she would have to start labor inflight. If her water breaks on the plane seat, the flight attendants will hopefully let a pilot know to divert to the nearest airport, which should be about 15 minutes to an hour away in the US. (Theoretically she could deliver inflight.)