Isn't the both parents required to be there to stop kidnapping and other issues?
Other countries might require presence or a signed affidavit from both parents when the child is actually flying out of the country.
My mom had custody but her bio dad and his wife kept kidnapping her and taking her across state lines.
At one point the dad was at the airport with a shotgun waiting for them. Police had to sneak my parents onto a plane.
Eventually my mom just walked with for several years at school never letting her out of her sight. That stopped at least one attempt, maybe more.