diff --git a/pkg/asset/installconfig/gcp/validation.go b/pkg/asset/installconfig/gcp/validation.go
index b3b3d612cba..b5569d6a337 100644
--- a/pkg/asset/installconfig/gcp/validation.go
+++ b/pkg/asset/installconfig/gcp/validation.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"net/http"
 	"slices"
 	"strings"
 
@@ -201,11 +202,16 @@ func validateDiskTypeAvailability(client API, fieldPath *field.Path, project, re
 
 	dt, dtZones, err := client.GetDiskTypeWithZones(context.TODO(), project, region, diskType)
 	if err != nil {
+		// Reading a disk type is not required to install, so a service account
+		// holding only the minimum set of install permissions is denied here. That
+		// says nothing about the configured disk type, so skip the check rather
+		// than report a bad value.
 		var gerr *googleapi.Error
-		if errors.As(err, &gerr) {
+		if errors.As(err, &gerr) && gerr.Code < 500 && gerr.Code != http.StatusForbidden {
 			return append(allErrs, field.Invalid(fieldPath.Child("diskType"), diskType, err.Error()))
 		}
-		return append(allErrs, field.InternalError(fieldPath.Child("diskType"), err))
+		logrus.Warnf("could not verify disk type %s availability in %s, skipping API check: %v", diskType, region, err)
+		return allErrs
 	}
 
 	if dt == nil {
diff --git a/pkg/asset/installconfig/gcp/validation_test.go b/pkg/asset/installconfig/gcp/validation_test.go
index 601b232f3fb..7b31a7a78da 100644
--- a/pkg/asset/installconfig/gcp/validation_test.go
+++ b/pkg/asset/installconfig/gcp/validation_test.go
@@ -1465,6 +1465,7 @@ func TestValidateDiskTypeAvailability(t *testing.T) {
 		mockErr        error
 		expectedError  bool
 		expectedErrMsg string
+		expectedWarn   string
 	}{
 		{
 			name:          "Empty disk type is a no-op",
@@ -1509,21 +1510,33 @@ func TestValidateDiskTypeAvailability(t *testing.T) {
 		{
 			name:           "GCP API error returns field error",
 			diskType:       "pd-ssd",
-			mockErr:        &googleapi.Error{Code: http.StatusForbidden, Message: "forbidden"},
+			mockErr:        &googleapi.Error{Code: http.StatusBadRequest, Message: "bad request"},
 			expectedError:  true,
-			expectedErrMsg: `forbidden`,
+			expectedErrMsg: `bad request`,
 		},
 		{
-			name:           "Non-API error returns internal error",
-			diskType:       "pd-ssd",
-			mockErr:        fmt.Errorf("network timeout"),
-			expectedError:  true,
-			expectedErrMsg: `network timeout`,
+			name:         "GCP 403 permission denied degrades gracefully",
+			diskType:     "pd-ssd",
+			mockErr:      &googleapi.Error{Code: http.StatusForbidden, Message: "Required 'compute.diskTypes.get' permission"},
+			expectedWarn: `could not verify disk type pd-ssd availability`,
+		},
+		{
+			name:         "GCP 503 server error degrades gracefully",
+			diskType:     "pd-ssd",
+			mockErr:      &googleapi.Error{Code: http.StatusServiceUnavailable, Message: "backend error"},
+			expectedWarn: `could not verify disk type pd-ssd availability`,
+		},
+		{
+			name:         "Non-API error degrades gracefully",
+			diskType:     "pd-ssd",
+			mockErr:      fmt.Errorf("network timeout"),
+			expectedWarn: `could not verify disk type pd-ssd availability`,
 		},
 	}
 
 	for _, test := range cases {
 		t.Run(test.name, func(t *testing.T) {
+			hook := logrusTest.NewGlobal()
 			mockCtrl := gomock.NewController(t)
 			defer mockCtrl.Finish()
 			gcpClient := mock.NewMockAPI(mockCtrl)
@@ -1539,6 +1552,10 @@ func TestValidateDiskTypeAvailability(t *testing.T) {
 			} else {
 				assert.Empty(t, errs)
 			}
+			if test.expectedWarn != "" {
+				assert.NotEmpty(t, hook.Entries)
+				assert.Regexp(t, test.expectedWarn, hook.LastEntry().Message)
+			}
 		})
 	}
 }