[crescentfresh]

The affected zone is use1-az4. Whatever that maps to (1a, 1b, 1c) is different per customer.

[benedikt]

you can find out which zone is mapped to use1-az4 for your account with awscli:

    aws ec2 describe-availability-zones | jq -r '.AvailabilityZones[] | select(.ZoneId == "use1-az4") | .ZoneName'

[mnordhoff]

Or if you open the EC2 console (it's up this time!) and scroll down to the bottom.

https://console.aws.amazon.com/ec2/v2/home?region=us-east-1#...:

(Edit: I hope I didn't sound sarcastic. I don't open random console pages and scroll all the way down to check for new features. Some people will have noticed, some won't.)