Originally Posted by
joeypore
(do you call the airline to confirm the reason?)
If your delay involves AA, all you need to do is submit this form:
https://www.aa.com/contact/forms?topic=TRP#/
That link should take you right here, with Trip Insurance Verification already pre-selected:
It'll take them ballpark 10 days to get back to you, but you'll get an emailed letter that you can provide to Amex. (Worked for me when I had a diversion last year.)
Not sure how to get something similar from WN or other airlines. I presume you can call/email their customer service if necessary.