For what's it worth...The Captain has final authority onboard and has to consider the safety of his crew members and passengers...As a Consultant for several airlines in Passenger Disability I can attest that there have been several incidents involving the DPNA SSR that have been both favorable and unfavorable. The Airlines are required to make sure the DPNA has an "escort" or a represenative making sure things are fine between connecting flights and et cetera kind of like a WHCR but there have been some documented incidents of denied boarding due to the DPNA being "unfit" to fly at the time of the flight.