The Leonardo service to Fiumicino is guaranteed during strikes and other disruption.
In exceptional circumstances that guarantee is a replacement bus. I'm hoping exceptional means problems with the line, not strikes - but we're going for an earlier train than planned just in case (Rome traffic...
As I understand it there is a rail strike on Friday 8th. It's a separate entry to the "excluding transport" one @Stat Brother posted earlier on this thread.
I believe the Leonardo Express to Fiumicino airport should still run as that's part of the minimum agreed service during strikes. But...