diff --git a/data/data/aws/bootstrap/variables.tf b/data/data/aws/bootstrap/variables.tf
index faed48e1fbe..3e93ae85fce 100644
--- a/data/data/aws/bootstrap/variables.tf
+++ b/data/data/aws/bootstrap/variables.tf
@@ -15,8 +15,7 @@ variable "ignition" {
 
 variable "instance_type" {
   type        = "string"
-  default     = "m4.large"
-  description = "The EC2 instance type for the bootstrap node."
+  description = "The instance type of the bootstrap node."
 }
 
 variable "subnet_id" {
diff --git a/data/data/aws/main.tf b/data/data/aws/main.tf
index 14161edd4ba..7bed29d893e 100644
--- a/data/data/aws/main.tf
+++ b/data/data/aws/main.tf
@@ -16,6 +16,7 @@ module "bootstrap" {
   source = "./bootstrap"
 
   ami                      = "${var.aws_ec2_ami_override}"
+  instance_type            = "${var.aws_bootstrap_instance_type}"
   cluster_name             = "${var.cluster_name}"
   ignition                 = "${var.ignition_bootstrap}"
   subnet_id                = "${module.vpc.public_subnet_ids[0]}"
@@ -32,9 +33,9 @@ module "bootstrap" {
 module "masters" {
   source = "./master"
 
-  cluster_id   = "${var.cluster_id}"
-  cluster_name = "${var.cluster_name}"
-  ec2_type     = "${var.aws_master_ec2_type}"
+  cluster_id    = "${var.cluster_id}"
+  cluster_name  = "${var.cluster_name}"
+  instance_type = "${var.aws_master_instance_type}"
 
   tags = "${merge(map(
       "kubernetes.io/cluster/${var.cluster_name}", "owned",
diff --git a/data/data/aws/master/main.tf b/data/data/aws/master/main.tf
index 232c8594601..54404822ba1 100644
--- a/data/data/aws/master/main.tf
+++ b/data/data/aws/master/main.tf
@@ -71,7 +71,7 @@ resource "aws_instance" "master" {
   ami   = "${var.ec2_ami}"
 
   iam_instance_profile = "${aws_iam_instance_profile.master.name}"
-  instance_type        = "${var.ec2_type}"
+  instance_type        = "${var.instance_type}"
   subnet_id            = "${element(var.subnet_ids, count.index)}"
   user_data            = "${var.user_data_ign}"
 
diff --git a/data/data/aws/master/variables.tf b/data/data/aws/master/variables.tf
index 6f536718b8b..050f93f4721 100644
--- a/data/data/aws/master/variables.tf
+++ b/data/data/aws/master/variables.tf
@@ -11,7 +11,7 @@ variable "dns_server_ip" {
   default = ""
 }
 
-variable "ec2_type" {
+variable "instance_type" {
   type = "string"
 }
 
diff --git a/data/data/aws/variables-aws.tf b/data/data/aws/variables-aws.tf
index 630e3eb65d2..e7530e54374 100644
--- a/data/data/aws/variables-aws.tf
+++ b/data/data/aws/variables-aws.tf
@@ -7,9 +7,14 @@ EOF
   default = "1.0"
 }
 
-variable "aws_master_ec2_type" {
+variable "aws_bootstrap_instance_type" {
   type        = "string"
-  description = "Instance size for the master node(s). Example: `m4.large`."
+  description = "Instance type for the bootstrap node. Example: `m4.large`."
+}
+
+variable "aws_master_instance_type" {
+  type        = "string"
+  description = "Instance type for the master node(s). Example: `m4.large`."
 }
 
 variable "aws_ec2_ami_override" {
diff --git a/pkg/asset/machines/master.go b/pkg/asset/machines/master.go
index 4ab7a5aa05f..14914d865c9 100644
--- a/pkg/asset/machines/master.go
+++ b/pkg/asset/machines/master.go
@@ -17,6 +17,7 @@ import (
 	"github.com/openshift/installer/pkg/asset/machines/openstack"
 	"github.com/openshift/installer/pkg/asset/rhcos"
 	awstypes "github.com/openshift/installer/pkg/types/aws"
+	awsdefaults "github.com/openshift/installer/pkg/types/aws/defaults"
 	libvirttypes "github.com/openshift/installer/pkg/types/libvirt"
 	nonetypes "github.com/openshift/installer/pkg/types/none"
 	openstacktypes "github.com/openshift/installer/pkg/types/openstack"
@@ -66,6 +67,12 @@ func (m *Master) Dependencies() []asset.Asset {
 	}
 }
 
+func awsDefaultMasterMachineType(installconfig *installconfig.InstallConfig) string {
+	region := installconfig.Config.Platform.AWS.Region
+	instanceClass := awsdefaults.InstanceClass(region)
+	return fmt.Sprintf("%s.xlarge", instanceClass)
+}
+
 // Generate generates the Master asset.
 func (m *Master) Generate(dependencies asset.Parents) error {
 	clusterID := &installconfig.ClusterID{}
@@ -81,7 +88,7 @@ func (m *Master) Generate(dependencies asset.Parents) error {
 	switch ic.Platform.Name() {
 	case awstypes.Name:
 		mpool := defaultAWSMachinePoolPlatform()
-		mpool.InstanceType = "m4.xlarge"
+		mpool.InstanceType = awsDefaultMasterMachineType(installconfig)
 		mpool.Set(ic.Platform.AWS.DefaultMachinePlatform)
 		mpool.Set(pool.Platform.AWS)
 		if len(mpool.Zones) == 0 {
diff --git a/pkg/asset/machines/worker.go b/pkg/asset/machines/worker.go
index 44b3e781ef7..fad164cd840 100644
--- a/pkg/asset/machines/worker.go
+++ b/pkg/asset/machines/worker.go
@@ -18,6 +18,7 @@ import (
 	"github.com/openshift/installer/pkg/asset/machines/openstack"
 	"github.com/openshift/installer/pkg/asset/rhcos"
 	awstypes "github.com/openshift/installer/pkg/types/aws"
+	awsdefaults "github.com/openshift/installer/pkg/types/aws/defaults"
 	libvirttypes "github.com/openshift/installer/pkg/types/libvirt"
 	nonetypes "github.com/openshift/installer/pkg/types/none"
 	openstacktypes "github.com/openshift/installer/pkg/types/openstack"
@@ -70,6 +71,12 @@ func (w *Worker) Dependencies() []asset.Asset {
 	}
 }
 
+func awsDefaultWorkerMachineType(installconfig *installconfig.InstallConfig) string {
+	region := installconfig.Config.Platform.AWS.Region
+	instanceClass := awsdefaults.InstanceClass(region)
+	return fmt.Sprintf("%s.large", instanceClass)
+}
+
 // Generate generates the Worker asset.
 func (w *Worker) Generate(dependencies asset.Parents) error {
 	clusterID := &installconfig.ClusterID{}
@@ -92,7 +99,7 @@ func (w *Worker) Generate(dependencies asset.Parents) error {
 		switch ic.Platform.Name() {
 		case awstypes.Name:
 			mpool := defaultAWSMachinePoolPlatform()
-			mpool.InstanceType = "m4.large"
+			mpool.InstanceType = awsDefaultWorkerMachineType(installconfig)
 			mpool.Set(ic.Platform.AWS.DefaultMachinePlatform)
 			mpool.Set(pool.Platform.AWS)
 			if len(mpool.Zones) == 0 {
diff --git a/pkg/tfvars/aws/aws.go b/pkg/tfvars/aws/aws.go
index 2e932158048..a5fb07c4a88 100644
--- a/pkg/tfvars/aws/aws.go
+++ b/pkg/tfvars/aws/aws.go
@@ -3,19 +3,22 @@ package aws
 
 import (
 	"encoding/json"
+	"fmt"
 
+	"github.com/openshift/installer/pkg/types/aws/defaults"
 	"github.com/pkg/errors"
 	"sigs.k8s.io/cluster-api-provider-aws/pkg/apis/awsproviderconfig/v1beta1"
 )
 
 type config struct {
-	EC2AMIOverride string            `json:"aws_ec2_ami_override,omitempty"`
-	ExtraTags      map[string]string `json:"aws_extra_tags,omitempty"`
-	EC2Type        string            `json:"aws_master_ec2_type,omitempty"`
-	IOPS           int64             `json:"aws_master_root_volume_iops"`
-	Size           int64             `json:"aws_master_root_volume_size,omitempty"`
-	Type           string            `json:"aws_master_root_volume_type,omitempty"`
-	Region         string            `json:"aws_region,omitempty"`
+	EC2AMIOverride        string            `json:"aws_ec2_ami_override,omitempty"`
+	ExtraTags             map[string]string `json:"aws_extra_tags,omitempty"`
+	BootstrapInstanceType string            `json:"aws_bootstrap_instance_type,omitempty"`
+	MasterInstanceType    string            `json:"aws_master_instance_type,omitempty"`
+	IOPS                  int64             `json:"aws_master_root_volume_iops"`
+	Size                  int64             `json:"aws_master_root_volume_size,omitempty"`
+	Type                  string            `json:"aws_master_root_volume_type,omitempty"`
+	Region                string            `json:"aws_region,omitempty"`
 }
 
 // TFVars generates AWS-specific Terraform variables launching the cluster.
@@ -46,13 +49,16 @@ func TFVars(masterConfig *v1beta1.AWSMachineProviderConfig) ([]byte, error) {
 		return nil, errors.New("EBS IOPS must be configured for the io1 root volume")
 	}
 
+	instanceClass := defaults.InstanceClass(masterConfig.Placement.Region)
+
 	cfg := &config{
-		Region:         masterConfig.Placement.Region,
-		ExtraTags:      tags,
-		EC2AMIOverride: *masterConfig.AMI.ID,
-		EC2Type:        masterConfig.InstanceType,
-		Size:           *rootVolume.EBS.VolumeSize,
-		Type:           *rootVolume.EBS.VolumeType,
+		Region:                masterConfig.Placement.Region,
+		ExtraTags:             tags,
+		EC2AMIOverride:        *masterConfig.AMI.ID,
+		BootstrapInstanceType: fmt.Sprintf("%s.large", instanceClass),
+		MasterInstanceType:    masterConfig.InstanceType,
+		Size:                  *rootVolume.EBS.VolumeSize,
+		Type:                  *rootVolume.EBS.VolumeType,
 	}
 
 	if rootVolume.EBS.Iops != nil {
diff --git a/pkg/types/aws/defaults/platform.go b/pkg/types/aws/defaults/platform.go
index 273ae07bdc9..08f986734ee 100644
--- a/pkg/types/aws/defaults/platform.go
+++ b/pkg/types/aws/defaults/platform.go
@@ -4,6 +4,24 @@ import (
 	"github.com/openshift/installer/pkg/types/aws"
 )
 
+var (
+	defaultMachineClass = map[string]string{
+		"eu-north-1":    "m5",
+		"eu-west-3":     "m5",
+		"us-gov-east-1": "m5",
+	}
+)
+
 // SetPlatformDefaults sets the defaults for the platform.
 func SetPlatformDefaults(p *aws.Platform) {
 }
+
+// InstanceClass returns the instance "class" we should use for a given
+// region. We prefer m4 if available (more EBS volumes per node) but will use
+// m5 in regions that don't have m4.
+func InstanceClass(region string) string {
+	if class, ok := defaultMachineClass[region]; ok {
+		return class
+	}
+	return "m4"
+}
diff --git a/pkg/types/aws/validation/platform.go b/pkg/types/aws/validation/platform.go
index a231372b9bd..f2f2c058867 100644
--- a/pkg/types/aws/validation/platform.go
+++ b/pkg/types/aws/validation/platform.go
@@ -23,12 +23,15 @@ var (
 		"cn-north-1":     "Beijing",
 		"cn-northwest-1": "Ningxia",
 		"eu-central-1":   "Frankfurt",
+		"eu-north-1":     "Stockholm",
 		"eu-west-1":      "Ireland",
 		"eu-west-2":      "London",
 		"eu-west-3":      "Paris",
 		"sa-east-1":      "São Paulo",
 		"us-east-1":      "N. Virginia",
 		"us-east-2":      "Ohio",
+		"us-gov-east-1":  "AWS GovCloud (US-East)",
+		"us-gov-west-1":  "AWS GovCloud (US-West)",
 		"us-west-1":      "N. California",
 		"us-west-2":      "Oregon",
 	}
diff --git a/pkg/types/validation/installconfig_test.go b/pkg/types/validation/installconfig_test.go
index 900104a1760..f91b895eff8 100644
--- a/pkg/types/validation/installconfig_test.go
+++ b/pkg/types/validation/installconfig_test.go
@@ -290,7 +290,7 @@ func TestValidateInstallConfig(t *testing.T) {
 				}
 				return c
 			}(),
-			expectedError: `^platform\.aws\.region: Unsupported value: "": supported values: "ap-northeast-1", "ap-northeast-2", "ap-northeast-3", "ap-south-1", "ap-southeast-1", "ap-southeast-2", "ca-central-1", "cn-north-1", "cn-northwest-1", "eu-central-1", "eu-west-1", "eu-west-2", "eu-west-3", "sa-east-1", "us-east-1", "us-east-2", "us-west-1", "us-west-2"$`,
+			expectedError: `^platform\.aws\.region: Unsupported value: "": supported values: "ap-northeast-1", "ap-northeast-2", "ap-northeast-3", "ap-south-1", "ap-southeast-1", "ap-southeast-2", "ca-central-1", "cn-north-1", "cn-northwest-1", "eu-central-1", "eu-north-1", "eu-west-1", "eu-west-2", "eu-west-3", "sa-east-1", "us-east-1", "us-east-2", "us-gov-east-1", "us-gov-west-1", "us-west-1", "us-west-2"$`,
 		},
 		{
 			name: "valid libvirt platform",
diff --git a/platformtests/README.md b/platformtests/README.md
new file mode 100644
index 00000000000..9f05880656f
--- /dev/null
+++ b/platformtests/README.md
@@ -0,0 +1,9 @@
+# Platform Tests
+
+This directory contains test suites checking per-platform assumptions.
+These tests require platform access that is not appropriate for platform-agnostic unit tests.
+The `t` directory name (unlike `tests`) allows us to share [the project `vendor` directory managed by `dep`](../docs/dev/dependencies.md#go).
+
+Platforms:
+
+* [aws](aws)
diff --git a/platformtests/aws/README.md b/platformtests/aws/README.md
new file mode 100644
index 00000000000..e090126a376
--- /dev/null
+++ b/platformtests/aws/README.md
@@ -0,0 +1,12 @@
+# AWS Tests
+
+This directory contains test suites checking AWS-specific assumptions.
+Run with:
+
+```console
+$ AWS_PROFILE=your-profile go test .
+```
+
+or similar (it needs access to [your AWS credentials][credentials]).
+
+[credentials]: https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html
diff --git a/platformtests/aws/default_instance_class_test.go b/platformtests/aws/default_instance_class_test.go
new file mode 100644
index 00000000000..b1b78440144
--- /dev/null
+++ b/platformtests/aws/default_instance_class_test.go
@@ -0,0 +1,110 @@
+package aws
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/pricing"
+	awsutil "github.com/openshift/installer/pkg/asset/installconfig/aws"
+	"github.com/openshift/installer/pkg/types/aws/defaults"
+	"github.com/openshift/installer/pkg/types/aws/validation"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetDefaultInstanceClass(t *testing.T) {
+	ssn, err := awsutil.GetSession()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	exists := struct{}{}
+	instanceClasses := map[string]map[string]struct{}{}
+
+	client := pricing.New(ssn, aws.NewConfig().WithRegion("us-east-1"))
+
+	err = client.GetProductsPages(
+		&pricing.GetProductsInput{
+			ServiceCode: aws.String("AmazonEC2"),
+			Filters: []*pricing.Filter{
+				{
+					Field: aws.String("tenancy"),
+					Type:  aws.String("TERM_MATCH"),
+					Value: aws.String("Shared"),
+				},
+				{
+					Field: aws.String("productFamily"),
+					Type:  aws.String("TERM_MATCH"),
+					Value: aws.String("Compute Instance"),
+				},
+				{
+					Field: aws.String("operatingSystem"),
+					Type:  aws.String("TERM_MATCH"),
+					Value: aws.String("Linux"),
+				},
+				{
+					Field: aws.String("instanceFamily"),
+					Type:  aws.String("TERM_MATCH"),
+					Value: aws.String("General purpose"),
+				},
+			},
+		},
+		func(result *pricing.GetProductsOutput, lastPage bool) bool {
+			for _, priceList := range result.PriceList {
+				product := priceList["product"].(map[string]interface{})
+				attr := product["attributes"].(map[string]interface{})
+				location := attr["location"].(string)
+				instanceType := attr["instanceType"].(string)
+				instanceClassSlice := strings.Split(instanceType, ".")
+				instanceClass := instanceClassSlice[0]
+				_, ok := instanceClasses[location]
+				if ok {
+					instanceClasses[location][instanceClass] = exists
+				} else {
+					instanceClasses[location] = map[string]struct{}{instanceClass: exists}
+				}
+			}
+			return !lastPage
+		},
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	regions := map[string]string{ // seed with locations that don't match AWS's usual names
+		"South America (Sao Paulo)": "sa-east-1",
+		"AWS GovCloud (US)":         "us-gov-west-1",
+	}
+
+	for location, classes := range instanceClasses {
+		t.Run(location, func(t *testing.T) {
+			region, ok := regions[location]
+			if !ok {
+				for slug, name := range validation.Regions {
+					if strings.Contains(location, name) {
+						regions[location] = slug
+						region = slug
+						break
+					}
+				}
+				if region == "" {
+					t.Fatal("not a recognized region")
+				}
+			}
+
+			class := ""
+			// ordered list of prefered instance classes
+			for _, preferredClass := range []string{"m4", "m5"} {
+				if _, ok := classes[preferredClass]; ok {
+					class = preferredClass
+					break
+				}
+			}
+			if class == "" {
+				t.Fatalf("does not support any preferred classes: %v", classes)
+			}
+			defaultClass := defaults.InstanceClass(region)
+			assert.Equal(t, defaultClass, class)
+		})
+	}
+}