This is one of the ways that I use iNat as well! I love being a passenger on road trips, as I can take pictures of things like Eastern White Pines and Turkey Vultures to help map out my travels in between stops.
That of course means I also try to document as much as I can at airports, although it rarely results in much exciting. One exception was at the Punta Cana airport, where they had an outside areas for smokers that had a flowering tree filled with butterflies and bees and where I got my lifer Dingy Purplewings: https://www.inaturalist.ca/observations/323249256
Ir is sort of a way to pass time, specially when you visit many airport too often, they eventually become the same.
So challenging yourself to find any verifiable observations is great activity 
As I said, I don’t fly often and if, within Europe it’s a direct flight, so no new places on my personal map. But I just remembered an incident when I took a night bus from Madrid to Sevilla and we stopped at a rest-area at 2 a.m. Walking around the brightly lit house I found 5 moths of 4 species! I was very much awake afterwards.
https://www.inaturalist.org/observations?on=2022-05-03&subview=table&user_id=susanne-kasimir&verifiable=any
I got a Double-striped Thick Knee when taking a video of my plane taking off
https://www.inaturalist.org/observations/212164524
First I thought: what kind of strange disease is that? I’ve heard of tennis arm… 
Cool observation!
I don’t usually manage to observe anything within airports, but definitely when walking to and from them. And the time spent waiting is often spent uploading my backlog of observations.
Yes. My last trip, I had a layover with a hotel stay. The hotel was on the edge of a large natural area. I got a lot of great observations.
Yes, and eBirding too, specially when visiting an airport for the first time.
I must say that the JFK International Airport was an absolute challenge, as I spent almost an hour looking for something. What a desert! But I managed to find a pigeon far away. Yay (?).
And not just in those big city airports. I now live in Costa Rica in retirement and on one of my nature photography trips to a rainforest I was returning on a small Sansa plane and while waiting in the tiny Golfito terminal I photographed a butterfly that I had not seen anywhere else and still haven’t seen that species. Always be alert for new species! 
Yup. Anytime, anywhere, especially when I have nothing but time. Got a few at the Seattle, Cancun and La Palma airports for sure.