diff --git a/QGCExternalLibs.pri b/QGCExternalLibs.pri
index a49f5b029ff8a478e8b7357b2b5843796e3bf3ec..dd8a36f7eab065a6a8e312f0264de233aa389cf8 100644
--- a/QGCExternalLibs.pri
+++ b/QGCExternalLibs.pri
@@ -108,6 +108,14 @@ SOURCES += \
     libs/shapelib/shpopen.c \
     libs/shapelib/safileio.c
 
+#
+# [REQUIRED] zlib library
+Windows {
+    INCLUDEPATH +=  $$SOURCE_DIR/libszlib/windows/include
+    LIBS += -L$$SOURCE_DIR/libszlib/windows/lib
+}
+LIBS += -lz
+
 #
 # [REQUIRED] SDL dependency. Provides joystick/gamepad support.
 # The SDL is packaged with QGC for the Mac and Windows. Linux support requires installing the SDL
@@ -143,7 +151,7 @@ contains(DEFINES, QGC_ENABLE_PAIRING) {
         exists(/usr/local/Cellar/openssl/1.0.2t/include) {
             INCLUDEPATH += /usr/local/Cellar/openssl/1.0.2t/include
             LIBS += -L/usr/local/Cellar/openssl/1.0.2t/lib
-            LIBS += -lcrypto -lz
+            LIBS += -lcrypto
         } else {
             # There is some circular reference settings going on between QGCExternalLibs.pri and gqgroundcontrol.pro.
             # So this duplicates some of the enable/disable logic which would normally be in qgroundcontrol.pro.
@@ -153,7 +161,7 @@ contains(DEFINES, QGC_ENABLE_PAIRING) {
         #- Pairing is not supported on Windows
         DEFINES -= QGC_ENABLE_PAIRING
     } else {
-        LIBS += -lcrypto -lz
+        LIBS += -lcrypto
         AndroidBuild {
             contains(QT_ARCH, arm) {
                 LIBS += $$ANDROID_EXTRA_LIBS
diff --git a/src/VehicleSetup/FirmwareUpgradeController.cc b/src/VehicleSetup/FirmwareUpgradeController.cc
index 7ce4935ac1bea12a50440e468e3396941efc457d..149c7248f4600044de857ceae81aedac7577230e 100644
--- a/src/VehicleSetup/FirmwareUpgradeController.cc
+++ b/src/VehicleSetup/FirmwareUpgradeController.cc
@@ -9,13 +9,13 @@
 
 #include "FirmwareUpgradeController.h"
 #include "Bootloader.h"
-//-- TODO: #include "QGCQFileDialog.h"
 #include "QGCApplication.h"
 #include "QGCFileDownload.h"
 #include "QGCOptions.h"
 #include "QGCCorePlugin.h"
 #include "FirmwareUpgradeSettings.h"
 #include "SettingsManager.h"
+#include "QGCTemporaryFile.h"
 
 #include <QStandardPaths>
 #include <QRegularExpression>
@@ -24,6 +24,8 @@
 #include <QJsonArray>
 #include <QNetworkProxy>
 
+#include "zlib.h"
+
 const char* FirmwareUpgradeController::_manifestFirmwareJsonKey =               "firmware";
 const char* FirmwareUpgradeController::_manifestBoardIdJsonKey =                "board_id";
 const char* FirmwareUpgradeController::_manifestMavTypeJsonKey =                "mav-type";
@@ -878,11 +880,7 @@ void FirmwareUpgradeController::_downloadArduPilotManifest(void)
     QGCFileDownload* downloader = new QGCFileDownload(this);
     connect(downloader, &QGCFileDownload::downloadFinished, this, &FirmwareUpgradeController::_ardupilotManifestDownloadFinished);
     connect(downloader, &QGCFileDownload::error,            this, &FirmwareUpgradeController::_ardupilotManifestDownloadError);
-#if 0
     downloader->download(QStringLiteral("http://firmware.ardupilot.org/manifest.json.gz"));
-#else
-    downloader->download(QStringLiteral("http://firmware.ardupilot.org/manifest.json"));
-#endif
 }
 
 void FirmwareUpgradeController::_ardupilotManifestDownloadFinished(QString remoteFile, QString localFile)
@@ -892,49 +890,70 @@ void FirmwareUpgradeController::_ardupilotManifestDownloadFinished(QString remot
     // Delete the QGCFileDownload object
     sender()->deleteLater();
 
-    qDebug() << "_ardupilotManifestDownloadFinished" << remoteFile << localFile;
+    qCDebug(FirmwareUpgradeLog) << "_ardupilotManifestDownloadFinished" << remoteFile << localFile;
 
-#if 0
-    QFile gzipFile(localFile);
-    if (!gzipFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
-        qCWarning(FirmwareUpgradeLog) << "Unable to open ArduPilot firmware manifest file" << localFile << gzipFile.errorString();
+    QFile inputFile(localFile);
+    if (!inputFile.open(QIODevice::ReadOnly)) {
+        qCWarning(FirmwareUpgradeLog) << "Unable to open ArduPilot firmware manifest file for reading" << localFile << inputFile.errorString();
         QFile::remove(localFile);
         return;
     }
 
-    // Store decompressed size as first four bytes. This is required by qUncompress routine.
-    QByteArray raw;
-    int decompressedSize = 3073444;
-    raw.append((unsigned char)((decompressedSize >> 24) & 0xFF));
-    raw.append((unsigned char)((decompressedSize >> 16) & 0xFF));
-    raw.append((unsigned char)((decompressedSize >> 8) & 0xFF));
-    raw.append((unsigned char)((decompressedSize >> 0) & 0xFF));
-
-    raw.append(gzipFile.readAll());
-    QByteArray bytes = qUncompress(raw);
-#else
-
-
-    QFile jsonFile(localFile);
-    if (!jsonFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
-        qCWarning(FirmwareUpgradeLog) << "Unable to open ArduPilot firmware manifest file" << localFile << jsonFile.errorString();
+    int             ret;
+    const int       cBuffer = 1024 * 5;
+    unsigned char   inputBuffer[cBuffer];
+    unsigned char   outputBuffer[cBuffer];
+    z_stream        strm;
+    QByteArray      jsonBytes;
+
+    strm.zalloc     = nullptr;
+    strm.zfree      = nullptr;
+    strm.opaque     = nullptr;
+    strm.avail_in   = 0;
+    strm.next_in    = nullptr;
+
+    ret = inflateInit2(&strm, 16+MAX_WBITS);
+    if (ret != Z_OK) {
+        qCWarning(FirmwareUpgradeLog) << "inflateInit2 failed:" << ret;
         QFile::remove(localFile);
         return;
     }
-    QByteArray bytes = jsonFile.readAll();
-    jsonFile.close();
-#endif
+
+    do {
+        strm.avail_in = static_cast<unsigned>(inputFile.read((char*)inputBuffer, cBuffer));
+        if (strm.avail_in == 0) {
+            break;
+        }
+        strm.next_in = inputBuffer;
+
+        do {
+            strm.avail_out  = cBuffer;
+            strm.next_out   = outputBuffer;
+
+            ret = inflate(&strm, Z_NO_FLUSH);
+            if (ret != Z_OK && ret != Z_STREAM_END) {
+                qCWarning(FirmwareUpgradeLog) << "Inflate failed" << ret;
+                inflateEnd(&strm);
+                QFile::remove(localFile);
+                return;
+            }
+
+            unsigned cBytesInflated = cBuffer - strm.avail_out;
+            jsonBytes.append((char*)outputBuffer, static_cast<int>(cBytesInflated));
+        } while (strm.avail_out == 0);
+    } while (ret != Z_STREAM_END);
+
+    inflateEnd(&strm);
+    inputFile.close();
     QFile::remove(localFile);
 
     QJsonParseError jsonParseError;
-    QJsonDocument doc = QJsonDocument::fromJson(bytes, &jsonParseError);
+    QJsonDocument doc = QJsonDocument::fromJson(jsonBytes, &jsonParseError);
     if (jsonParseError.error != QJsonParseError::NoError) {
         qCWarning(FirmwareUpgradeLog) <<  "Unable to open ArduPilot manifest json document" << localFile << jsonParseError.errorString();
     }
 
 
-
-
     QJsonObject json =          doc.object();
     QJsonArray  rgFirmware =    json[_manifestFirmwareJsonKey].toArray();