Usually, irrational and illogical mean the same thing. Occasionally they do not. If you phrase the question as "What is rational but illogical?" or "What is logical but irrational?" it becomes clearer. I'll try to provide an example of each.

If you're willing to accept loving one's spouse as rational, it falls under "rational but illogical" since logic has very little to do with emotion. That's on slightly shaky ground, but that's a good segue for the next example. If you start from an irrational premise ("pleasure is sinful") you can come to a logical but irrational conclusion ("women who have orgasms are sinners").

And, of course, now that I've commented I'll actually read the column. My response is that he's got it backwards. It is logical but irrational to fly separately. The irrational premise is that "the risk of orphaning your kids by both of you dying on the same plane flight is sufficient to act on." The logical but irrational conclusion is that you should not take the same flight as your spouse.

I don't think spliting the parents is such a logical idea either. You double the probability that the children will suffer the loss of a parent. And the remaining parent will go through considereable suffering. Whereas the children will still experience considerable suffering and life disruption from the loss of even one parent.

If you're really concerned about all that, then line up foster parents before something happens.

I agree with the above in regards to irrational vs. illogical. Logic is old-school 'if A and B therefore C' type stuff.

But rationality implies taking a much wider view of the world. And doing what makes sense given the facts. And the drive to get enough facts to make a good decision.

Irrational behavior is behavior which does not seek to fulfill your desires. Illogical behavior is behavior which does not obviously seek to fulfill your desires. ;)