Actually, I don't believe that the airlines are required to have emergency oxygen on board for medical emergencies. I don't know for sure though. Perhaps one of the pilot types could weigh in on it.
However, it seems like the family knew this woman was pretty ill. So for them to fail to make arrangements with the airline to have medical oxygen on board the aircraft seems to me to be the families fault, not the airlines. This is the information from
www.smartertravel.com:
According to the Transportation Security Administration (TSA), federal law prevents the airlines from allowing passengers to bring their own oxygen canisters, and there is no mandate requiring airlines to provide supplemental oxygen aboard. As a result, there is no oxygen provided on some low-cost carriers such as Southwest and JetBlue, or on certain regional or shuttle flights operated by the major airlines.
However, most of the legacy airlines, including American, United, Delta, US Airways, Northwest, and Continental, do offer in-flight oxygen on many routes, provided you give them at least 48 hours notice of your need and pay a hefty fee. Fees vary, but most airlines charge per flight segment. American, for example, charges $100 per segment, so if you were to book a round-trip flight with one connection each way, you'd pay a $400 fee. Airlines also usually require authorization from your doctor that supplemental oxygen is medically necessary.
Airlines do not provide oxygen on the ground, so you must make arrangements for friends, relatives, or local suppliers to bring you oxygen before departure, during layovers, between connecting flights, and after arrival. Oxygen is only allowed through security checkpoints after it passes x-ray and explosive trace detection screening.
To minimize hassles, plan your flights well in advance. Here are some tips:
Go to your airlines' website or call its customer service number to determine its policies regarding in-flight oxygen.
Talk to your doctor to obtain the necessary authorization and to make sure flying is safe for you.
When booking, try to reserve non-stop flights during off-peak hours if possible.
Visit the websites of the TSA and the National Home Oxygen Patient's Association for more detailed information about air travel with medical oxygen.