Edit based on the clarification that the website is to display information about an external crisis, not about web services going down:
If there is nothing wrong with your site or any of your web services during one of these crises (i.e. they are external crises you are reporting on like plane crashes, like you mentioned), I would recommend just having your important content just do a front-page takeover rather than using HTTP status codes. Have two versions of your home page - one for "normal" situations with your normal content, and one for your "important notice" situations where you replace whatever you usually have above-the-fold with a big eye-catching notice with your info feed. Serve it at the same URL (
/), because during a crisis, your home page IS the info page and it's just doing its job.
If the purpose of the page is to say something like "we're down for (planned/emergency) maintenance, but we'll be back soon", then this is a perfect use case for a 503 status code.
503 - Service Unavailable
The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.
I've seen this countless times on countless professional websites. It's industry standard and it's what Yoast recommends too:
503 Service unavailable. This is the one you want to be returning to Google when you’re dealing with site maintenance. It tells Google that you are in fact working on this page or that something else went wrong. Google knows that when this status code is returned, to check the page again later on.