United subscribes to Medlink, which provides on call, real-time medical assistance for emergencies in flight. They will indemnify and provide a defense to potential claims against physicians or other HC providers who assist with a medical emergency, with the caveat that the Medlink provider is in charge of the passenger's care until they are turned over to ground-based providers. Medlink providers will also offer voice guidance on divert/continue decisions but ultimately the call is the Captain's.

This is not legal advice, but for those concerned about liability, I encourage healthcare professionals I know to readily offer to assist if requested, but to defer to guidance by the Medlink provider because they have a policy specific to this situation with coverage primary to their own malpractice.

Often the best help that can be offered is basic patient assessment, and that information can be relayed to Medlink, which can marshal the proper resources to respond. It's unusual and exceedingly rare for any specialized care to be necessary.