AWS on demand ec2-instances, is availability checked across all Region Availability Zones

Question

I am trying to spin up a on demand d2.8xlarge instance in the us-east-1 region.

However for the past 2 days I have consistently received the error:

“We currently do not have sufficient d2.8xlarge capacity in the Availability Zone you requested (us-east-1c). Our system will be working on provisioning additional capacity. You can currently get d2.8xlarge capacity by not specifying an Availability Zone in your request or choosing us-east-1a,us-east-1b etc"

My question is:

I am not specifying an availability zone - I am only specifying the region "us-east-1" so is aws checking availability across all availability zones in the region specified or is it randomly choosing a availabilty zone to try within the region?

If it is choosing an availability zone in the region to try, how can I specify that it should try availability across all zones in my code which is as follows:

https://github.com/NREL/OpenStudio-server/blob/develop/bin/openstudio_meta#L761