Anyone else have issues with this?
Mine was working fine with the same macOS version - up until I got a new Mac - and now it's showing a trip I previously took (mid-May).
When I click on the widget, it says "Open Fly Delta on iPhone to continue".
I've logged out of everything, disabled/re-enabled Handoff, deleted Fly Delta, reinstalled, logged into Delta on Safari, used same network, different network, and it's still broken.

So did Delta screw up the handshake between new iOS app <> Mac widget, with the new Fly Delta app?

EDIT - I just tried on my iPhone - added and removed 5x - and the widget itself isn't pulling my itineraries - just "Find your escape - book now"