Some passengers board an aircraft with an underlying medical condition which makes flying inadvisable. Airline will try to screen such passengers and they have the right to stop them at the departure gate and refuse permission to embark. But unless the symptoms are very obvious, passengers at risk will remain undetected until it is too late. Sometimes the passengers themselves may not be aware of their own condition until a problem occurs. With the increase in leisure travel and particularly long haul travel by elderly passengers the likelihood of medical emergency during flight is on the increase. No airline would want to be seen to discriminate against the older generation so there is not much an airline can do about this other than following correct procedure when problem occurs.