diff --git a/html/config.js b/html/config.js
index a86d169..559e163 100644
--- a/html/config.js
+++ b/html/config.js
@@ -40,6 +40,7 @@
 
 // Color controls for the range outline
 //range_outline_color = '#0000DD';
+//range_outline_alpha = 1.0;
 //range_outline_width = 1.7;
 //range_outline_colored_by_altitude = false;
 //range_outline_dash = [5, 5]; // null - solid line, [5, 5] - dashed line with 5 pixel lines and spaces in between
diff --git a/html/defaults.js b/html/defaults.js
index 08f76cb..4c6fe5c 100644
--- a/html/defaults.js
+++ b/html/defaults.js
@@ -49,6 +49,7 @@ let updateLocation = false;
 
 // Color controls for the range outline
 let range_outline_color = '#0000DD';
+let range_outline_alpha = 1.0;
 let range_outline_width = 1.7;
 let range_outline_colored_by_altitude = false;
 let range_outline_dash = null; // null - solid line, [5, 5] - dashed line with 5 pixel lines and spaces in between
diff --git a/html/script.js b/html/script.js
index f0e9d44..693ddc8 100644
--- a/html/script.js
+++ b/html/script.js
@@ -6582,7 +6582,7 @@ function drawUpintheair() {
         let color = range_outline_color;
         if (range_outline_colored_by_altitude) {
             let colorArr = altitudeColor(altitude);
-            color = 'hsl(' + colorArr[0].toFixed(0) + ',' + colorArr[1].toFixed(0) + '%,' + colorArr[2].toFixed(0) + '%)';
+            color = 'hsla(' + colorArr[0].toFixed(0) + ',' + colorArr[1].toFixed(0) + '%,' + colorArr[2].toFixed(0) + '%,' + range_outline_alpha + ')';
         }
         let outlineStyle = new ol.style.Style({
             fill: null,