For the last few weeks we are having repeated connectivity issues. First it was the Cesium JS we were using from cesiumjs.org. This server stopped having a valid certificate and would break our map. We switched to cesium.com, and we plan on having a local copy to avoid connectivity issues with Cesium servers.
Today we are having a 503 (service unavailable) on our assets on Cesium ION.
As you experienced, there was a 10-minute Cesium ion outage today between 5:12AM - 5:22AM EDT (9:12AM - 9:22AM UTC) (see https://status.cesium.com/). After investigation, the root cause was found to be an AWS hardware failure that resulted in a brief loss of connectivity.
We’re pleased the infrastructure recovered so quickly, but understand it still impacted our users. Coming after your experience with the cesiumjs.org certificate, I see how this feels like a pattern, but this problem was an isolated incident, and availability issues for Cesium ion are rare. That said, we are always looking for ways to improve.