Very nice!
On my own carrier, they let us into first free, if available, but when I have traveled on other carrier's, they restrict us to coach....
I always get first on my carrier, but all we have are first class seats and bunks.
When deadheading international legs greater than three hours on passenger airlines we're contractually obligated to business class or better. This particular flight on Delta was LAX-SEA, so it was my status that got me the upgrade.
A few times when jumpseating I've managed to get first class. It's been more likely on RJs, but at least twice on mainline when the load was super light.