Flatcar Container Linux exits preview in AKS as of today. New node pools with Flatcar cannot be created from this point, and Microsoft will issue no further security patches for existing ones. The full code removal lands September 8 — after that, scaling and remediation operations on surviving Flatcar pools will fail outright. There is no in-place migration. Teams must spin up new node pools on Azure Linux or Ubuntu, shift workloads, and delete the old pools manually. Azure Linux is the Microsoft-maintained successor built specifically for AKS; Ubuntu is the portable option if cross-cloud compatibility matters more than optimization. September 8 is a real cliff — pools still running Flatcar past that date lose operational control entirely.