Comment 3 for bug 1733354

This has been fixed since 2.3-rc1.

5 pending pending xenial failed to start machine 5 in zone "us-east-1c", retrying in 10s with new availability zone: cannot run instances: Your requested instance type (m3.medium) is not supported in your requested Availability Zone (us-east-1c). Please retry your request by not specifying an Availability Zone or choosing us-east-1a, us-east-1b, us-east-1e, us-east-1d. (Unsupported)

(and then it tried us-east-1f, and failed again with the same error; and then tried us-east-1b, and succeeded)