Download this 1PIF (1Password Interchange Format) file and import it into 1Password. On the Mac you can do this by dragging the 1PIF file to the 1Password icon in the macOS dock. On Windows use the menu option 1Password > Import and follow the prompts.
Edit the newly imported Login item and click the Show Saved Form Details button. Replace the placeholder values for the three fields and set the remember me checkbox to whatever your preference is. I've set it as enabled in this Login item because it's much easier to delete the checkmark in 1Password for Windows than it is to add the right character. 1Password for Mac uses a real checkbox so nice and easy there.
After that all you should need to do is delete the redundant website field. I've added the two URLs from above so that out of the box it will fill either but most likely everybody will only use one based on their own needs.
This will fill both the homepage and the dedicated page for both domains. I've added URLs for the dedicated page so that open-and-fill can be used.
Where does the imperfection come in? On the US version of the site (
www.aa.com) It won't fill the fields correctly on the first attempt, it only fills the username and password. A second fill though sees the last name and checkbox correctly set. That's why the submit option has been set to Never so that the second fill can be performed.
Ideally there will be a version of 1Password where you can save and fill on American Airlines without all of this gymnastics but at least for now I hope this helps a little.