Amazon RDS for SQL Server now supports Always On Availability Groups for SQL Server 2017 which enables you to improve availability and durability of your SQL Server deployments by automatically replicating databases between two AWS Availability Zones (AZ). This feature is now available for SQL Server 2017 latest minor version (14.00.3049.1.v1) for the Enterprise Edition database engine. Previously, in November 2018, we announced support for this feature for SQL Server 2016 Enterprise Edition.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/05/amazon-rds-for-sql-server-now-supports-always-on-availability-groups-for-sql-server-2017/