When adding a monitor in California, I was given a dropdown to select from various airport codes in Oklahoma and Kansas.
I think this happened because MaxMind only provides country-level data for the IP in question, so the location lookup yielded airports in the geographic middle of the country.
It would be nice to have a text field to enter an airport code, in case the options in the dropdown are known by the user to be less accurate.
I was able to enter an airport code manually. I suspect the form has what Windows calls a dropdown combobox – an edit control with a dropdown where you can nonetheless manually type rather than select from the list. My terminology might be off because I’m not sure this was in fact a dropdown – I think the list was always visible.
Oh, I remember comboboxes from my Windows days, way back!
I just checked again for a new monitor though, and in Chrome on macOS it’s a regular, non-editable dropdown.
I had no trouble just typing one in, click the cursor in the lowest entry and type – I didn’t experiment a whole lot, but I did prefix the airport code with the two-letter country code and the list jumped right to the code I typed, even though it was not initially in the list at all.
@mopani which browser was that? It’s not an intentional feature, I don’t think, but maybe it’s the seeds of making it work.
@john1 (I think it was) had a similar issue with a generally geocoded IP, but the relevant country was smaller so there was a simple pragmatic fix in that case.
My goal is generally to make the system resilient (across all the components) and generally speaking that has worked out okay over the last 20 years.
This is a good example of trying to balance resilience through self-sufficiency and through boundaries on what people can do. It probably doesn’t matter if people use a weird or incorrect airport code, but in the first iteration of the new monitoring system some years ago I got burned by people volunteering to then point out in their research paper obvious problems with trusting people volunteering. (So, less trust since then I guess… 
)
I’m using Vivaldi (based on Chrome). I know for a fact that the IP address is wrongly geo-located, and USSLN is the closest airport I could easily identify since the data center is in Lenexa, KS (IONOS).
I’ve been impressed how well the system works overall, and I’m thrilled to see the improvements that have rolled out in the last five years I’ve been a member here. Thank you for the work you’ve done that benefits literally billions of people who have absolutely no clue why things work so well!