www.delta.com - Delta shows browser warning to Opera

**URL**: www.delta.com
**Browser / Version**: Opera 25
**Operating System**: Mac OS X 10.10.0
**Problem type**: Looks like the website has a bug.
**Site owner**: Unknown

**Steps to Reproduce**
1) Navigate to: www.delta.com

Expected Behavior:
I can use the site without seeing a browser warning.

Actual Behavior:
Browser warning is shown.