Physician here who flies a modest amount, although perhaps not as much as many people here do. :-)

I've responded to motor vehicle collisions a handful of times when I've come by them moments after they happened and EMS isn't there yet. My favorite was a car in a ditch where the solo driver was in the later stages of pregnancy. I would have done my best (she was awake and alert and doing okay, so no intervention called for yet), but then someone drove up and rolled down their window and said they were a physician. I said "So am I…what field are you in?" "OB/GYN." "I'm a pediatrician...she's pregnant and I'd love your help!" :-) (He was great, gave her good calming advice about getting checked out, etc etc.)

Anyhow, to public conveyances — I did have to respond on Amtrak once in the middle of a snowy Indiana rail yard. Chest pain, likely anxiety, but…man, the crew (this was 20+ years ago) didn't know they had a medical kit, and EMS couldn't figure how to get to us. Everything was fine in the end, but I was unimpressed.

The one notable incident I tended to in flight was about 3.5h out of SYD en route to LAX (yes, those setback monitors were showing an awful lot of blue around them). Young woman unconscious, only family traveling with her is her toddler. An emergency medicine physician also responded, and between the two of us, we tended to her. Long story short was she had a seizure, had forgotten to take her meds, and had the meds with her. He was talking to ground medical (sounds similar to Medlink), and all agreed she should simply take the meds once conscious. (Before we get too judgy, I also found out from her that she left the country hastily, fleeing a complicated social situation. It was almost comical, the other guy was true to form and worrying about all sorts of catastrophes like stroke and heart attack, and I, the primary care pediatrician got a good social history. :-) We made a good team.). All good, aside from filling out some paperwork. Crew were very, very appreciative.

Our nearest diversion options, apparently, were American Samoa (3h, not great ground facilities) and HNL (5h). Neither great if she had something more emergent, obviously. Luckily this was not, and we carried on the LAX without incident.

Two weeks later, I got an unexpected package at home. A box of nuts/crackers/jam/etc in a gift basket from DL, with a handwritten card thanking me for helping out. Nothing I asked for or even had a chance to turn down, of course.

I've been to those sessions at conferences — they're typically presented by lawyers or MD/JDs, and honestly, if I heard only those, I'd never get up. They're designed to offer you the most protective advice for you, the health care professional. But I do think there's a moral duty on some level, and even if you haven't done X or Y in a long long time, you likely know and remember more than any layperson does. Just think about what you're able to do or not do, and what advice or observations you can offer with what you do know. (And don't do what one of my braggy colleagues did and claim that "they turned the plane around" — that's the Captain's call, you idiot. *sigh*)

And the folks above in this thread who are sharing their gratitude and appreciation for someone out there having responded…yeah, that's what it comes down to.