PROBLEM:
A man and his son were traveling on a scheduled flight across the Atlantic.  The man asked the flight attendant if his son could have a look inside the cockpit.  The boy was allowed to do this and the pilot gladly explained about the plane and its controls.  After the boy left, the pilot turned to the co-pilot and said to him, "That was my son."

How could that be?.
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HINT 1:
Question: Were any stepfathers, grandparents, or in-law relationships involved?

Answer: No.
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HINT 2:
Question: Was the passenger the father of the pilot's son?

Answer: Yes.
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SOLUTION:
The pilot was the boy's mother.