Although they look sober and reliable, they hold a valid airline ticket, and don't look threatening, what category of people may be denied an airline seat?

It may seem surprising, but the primary concern that can lead to a passenger being denied boarding is the potential for an in-flight medical emergency. For women in the late stages of pregnancy, the risk of going into labor mid-flight is a significant consideration for airlines. An airplane at 35,000 feet is not equipped for childbirth, and diverting a flight for a medical emergency is a complex and costly operation that isn't always possible, especially over an ocean.

To mitigate this risk, most airlines have specific policies regarding travel for expectant mothers. While the rules vary by carrier, travel is often restricted after the 36-week mark for domestic flights and sometimes earlier, around 32 to 35 weeks, for international routes. Many airlines also require a doctor's note for travel after 28 weeks, which confirms the due date and certifies that the passenger is fit to fly without any known complications.

Ultimately, these policies are not meant to be discriminatory but are a safety-first measure. They are designed to protect the health and well-being of the mother and baby by avoiding a high-stakes medical situation in an environment with extremely limited resources. It also ensures the safety and schedule of the hundreds of other passengers on board by preventing a serious medical diversion.