Anecdotally, the highest altitude I've ever been at hiking was around 11,000ft, and the group I was hiking with started feeling it a little bit around 9000-10,000 ft.

It wasn't dramatic, where we really noticed it was after we'd made camp, we had a little downtime and there was a bit of an open area, so we started throwing around a Frisbee, and running around chasing the Frisbee we could feel we were getting winded a bit quicker than we usually would.

Age, fitness, genetics, etc. will of course factor into that, but I suspect that most reasonably healthy people sitting in an airplane probably wouldn't feel much at 7000ft. Maybe they would if they were jogging up and down the aisle of the plane, but even then it probably wouldn't be anything too obvious, and if they didn't know anything about altitude sickness they'd probably chalk it up to being tired from the mental stress of air travel- getting to the airport, making the connection, security, lost baggage, etc.

[–] Rivalarrival 5 points 4 days ago

and the group I was hiking with started feeling it a little bit around 9000-10,000 ft.

Hiking. Physical activity. You'll feel it a lot sooner than if you're just sitting in your seat, bored out of your skull.

Legally, the FAA doesn't require passengers to be on oxygen until cabin altitude is above 15,000 feet. Most aircraft are pressurized to the equivalent of 5000-7000 feet pressure altitude.

[–] PoliteDudeInTheMood@lemmy.ca 3 points 4 days ago

I was in Ecuador recently, Quito which is 9350ft. The second the plane door opened, I felt it. Leaving the plane the air was so thin I could barely stand up. The altitude sickness was alot more for me than "being tired". And I had started altitude sickness pills 2 days before my flight.