Depends on age and pre existing health of your parent.
Goastros, Hi. Personally if your Mom and dad are healthy, I would not get any insurance. You could just add on uninsured motorist on your car insurance or check with your auto insurance for coverage for co-travellers, in case of a wreck. Emergency room visits even for basic XRays could run up to a few thousand dollars. Without a high BP or Cholesterol or Sugar problem, the chances of something happening here in the U.S in a few months is negligible. YOU COULD USE THIS OPPURTUNITY TO HAVE THEM CHECKED OUT BY A LOCAL M.D IN YOUR COUNTRY, AND ALSO HAVE A STRESS TEST DONE BEFORE THEY BOARD THE FLIGHT.
My brother in law used a traveller insurance based in England , which actually paid big bucks for a heart attack his mother had while here in the U.S. I'll try to get that info for you.
Hope this helps.