Use cases - only ever for external actor's events

Hi, apologies if this question is dumb.

I’m modelling a system and trying to get my uml up to speed.

I’ve made use cases for all actor interaction with the system, but I’m wondering how I should model critical events in the system and highlight them to anyone reading my design.

As an example… modelling a airplane’s control systems. I’d have use cases for throttle back, applying rudders, pulling back on the stick etc as they are all pilot actions. But if I want to highlight another critical event like, say, running out of fuel or an oil pressure failure that’s not caused by an actor, what should I do please?

Thanks for any help,