
I arrived on this page to calculate international transit time for a FedEx package before sending it. The image shows the second step of the process. The first step involved selecting the two contries and the date of shipment.
I liked the fact that they seemed to have eliminated the "State" field, making it easier for me to enter just city and zip. But after I filled in the city, I learnt that the Zip field was actually optional. This was a bit annoying. Why is an Optional field blocking my way? An easy solution would be to move it alongside city.

The name of the city I entered is not unique so I'm required to select the correct one from given close matches. This is a clarification feature but why does FedEx displays it as an error message? Although they try to reduce the pain by taking an apologetic tone but it doesn't make sense. It's not their fault that there are 18 cities in the US with the name Austin!
I would not have gotten this error if the previous page carried a State field. Obviously, at some point in the design process a decision was made to keep State out of that page. Whether it was the correct decision should depend upon the uniqueness of an average city name entered in the field.
If most users get through to the next step without getting this message then it makes perfect sense, otherwise it's a bad decision. So I decided to conduct a little experiment to see what happens when I entered random city names. I collected names of five US cities from a listing of the safest cities in the country [#1-5] and tried each one on the form. After every attempt I took notes.
1. Amherst
There are 12 close matches
Yes Amherst, New York is present
2. Brick Township
There are 20 close matches but no Brick Township in New Jersey. Instead, I see three matches that are similar:
Brick, New Jersey
Brick Town, New Jersey
Bricktown, New Jersey
I don't know what a real user would do now. Clicking the Quick Help button opens a pop-up that doesn't help. [Note the previous page had a link for finding the Zip code for a location, to which I didn't pay any attention so it doesn't occur to me to head back. Even if I do head back, the link would offer no matches for Brick Township].
3. Mission Viejo
2 close matches
Mission Viejo, California is present.
4. Simi Valley
Bingo! I get a confirmed match.
5. Cary
6 close matches
Cary, North Carolina is present.
So, in 4 out of 5 cases I got the same error message and there were a total of 41 close matches for five cities. Clearly conclusive evidence that it's not a good idea to remove the State field on the form.
In view of the poor support for the city field, it also makes sense to prioritize Zip to a better position - entering zip eliminates the chance of an error. That doesn't mean making it mandatory which would cause further harm. It means making sure the user understands that entering Zip is a better option than just entering the name of the city.