diff --git a/simgear/io/HTTPClient.cxx b/simgear/io/HTTPClient.cxx
index 1126691c..86eeb6bc 100644
--- a/simgear/io/HTTPClient.cxx
+++ b/simgear/io/HTTPClient.cxx
@@ -35,8 +35,6 @@
 #include <stdexcept>
 #include <mutex>
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 #include <simgear/simgear_config.h>
 
 #include <curl/multi.h>
@@ -297,7 +295,7 @@ void Client::makeRequest(const Request_ptr& r)
       }
     }
 
-    std::string method = boost::to_lower_copy(r->method());
+    const std::string method = strutils::lowercase (r->method());
     if (method == "get") {
       curl_easy_setopt(curlRequest, CURLOPT_HTTPGET, 1);
     } else if (method == "put") {
@@ -530,8 +528,8 @@ size_t Client::requestHeaderCallback(char *rawBuffer, size_t size, size_t nitems
       return byteSize;
   }
 
-  std::string key = strutils::simplify(h.substr(0, colonPos));
-  std::string lkey = boost::to_lower_copy(key);
+  const std::string key = strutils::simplify(h.substr(0, colonPos));
+  const std::string lkey = strutils::lowercase (key);
   std::string value = strutils::strip(h.substr(colonPos + 1));
 
   req->responseHeader(lkey, value);
diff --git a/simgear/io/test_DNS.cxx b/simgear/io/test_DNS.cxx
index db99ae16..d9a52528 100644
--- a/simgear/io/test_DNS.cxx
+++ b/simgear/io/test_DNS.cxx
@@ -7,8 +7,6 @@
 #include <thread>
 #include <atomic>
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 #include <simgear/simgear_config.h>
 
 #include "DNSClient.hxx"
diff --git a/simgear/io/test_HTTP.cxx b/simgear/io/test_HTTP.cxx
index 601c1037..13723741 100644
--- a/simgear/io/test_HTTP.cxx
+++ b/simgear/io/test_HTTP.cxx
@@ -5,8 +5,6 @@
 #include <sstream>
 #include <cerrno>
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 #include <simgear/simgear_config.h>
 
 #include "HTTPClient.hxx"
diff --git a/simgear/io/test_HTTP.hxx b/simgear/io/test_HTTP.hxx
index f8dde98c..028b5dfc 100644
--- a/simgear/io/test_HTTP.hxx
+++ b/simgear/io/test_HTTP.hxx
@@ -1,6 +1,7 @@
 #ifndef SIMGEAR_IO_TEST_HTTP_HXX
 #define SIMGEAR_IO_TEST_HTTP_HXX
 
+#include <algorithm>
 #include <sstream>
 #include <vector>
 
diff --git a/simgear/io/test_repository.cxx b/simgear/io/test_repository.cxx
index 0148fc5c..9c641b77 100644
--- a/simgear/io/test_repository.cxx
+++ b/simgear/io/test_repository.cxx
@@ -5,8 +5,6 @@
 #include <errno.h>
 #include <fcntl.h>
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 #include <simgear/simgear_config.h>
 
 #include "test_HTTP.hxx"
diff --git a/simgear/io/text_DNS.cxx b/simgear/io/text_DNS.cxx
index cabc4813..14ae23e9 100644
--- a/simgear/io/text_DNS.cxx
+++ b/simgear/io/text_DNS.cxx
@@ -5,8 +5,6 @@
 #include <sstream>
 #include <errno.h>
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 #include <simgear/simgear_config.h>
 
 #include "HTTPClient.hxx"
diff --git a/simgear/misc/sg_path.cxx b/simgear/misc/sg_path.cxx
index a252480f..48d6b638 100644
--- a/simgear/misc/sg_path.cxx
+++ b/simgear/misc/sg_path.cxx
@@ -29,6 +29,7 @@
 #include <simgear/misc/strutils.hxx>
 #include <simgear/io/iostreams/sgstream.hxx>
 
+#include <cstring>
 #include <stdio.h>
 #include <sys/stat.h>
 #include <errno.h>
@@ -47,8 +48,6 @@
 
 #include "sg_path.hxx"
 
-#include <boost/algorithm/string/case_conv.hpp>
-
 using std::string;
 using simgear::strutils::starts_with;
 
@@ -398,7 +397,7 @@ string SGPath::extension() const {
 }
 
 string SGPath::lower_extension() const {
-    return boost::to_lower_copy(extension());
+    return simgear::strutils::lowercase (extension());
 }
 
 string SGPath::complete_lower_extension() const
@@ -412,7 +411,7 @@ string SGPath::complete_lower_extension() const
 
     string::size_type firstDot = path.find(".", index);
     if ((firstDot != string::npos)  && (path.find(sgDirPathSep, firstDot) == string::npos)) {
-        return boost::to_lower_copy(path.substr(firstDot + 1));
+        return simgear::strutils::lowercase (path.substr(firstDot + 1));
     } else {
         return "";
     }
diff --git a/simgear/package/Package.cxx b/simgear/package/Package.cxx
index a5fca6ce..8bc8e60a 100644
--- a/simgear/package/Package.cxx
+++ b/simgear/package/Package.cxx
@@ -20,7 +20,6 @@
 #include <simgear/package/Package.hxx>
 
 #include <cassert>
-#include <boost/algorithm/string/case_conv.hpp>
 
 #include <simgear/debug/logstream.hxx>
 #include <simgear/structure/exception.hxx>
@@ -44,8 +43,7 @@ void Package::initWithProps(const SGPropertyNode* aProps)
     m_props = const_cast<SGPropertyNode*>(aProps);
 // cache tag values
     for (auto c : aProps->getChildren("tag")) {
-      std::string t(c->getStringValue());
-      m_tags.insert(boost::to_lower_copy(t));
+      m_tags.insert (strutils::lowercase (c->getStringValue()));
     }
 
     m_id = m_props->getStringValue("id");
@@ -97,8 +95,7 @@ bool Package::matches(const SGPropertyNode* aFilter) const
     }
 
     if (filter_name == "tag") {
-        std::string tag(aFilter->getStringValue());
-        boost::to_lower(tag);
+        const std::string tag = strutils::lowercase (aFilter->getStringValue());
         return (m_tags.find(tag) != m_tags.end());
     }
 
@@ -110,18 +107,16 @@ bool Package::matches(const SGPropertyNode* aFilter) const
     // substring search of name, description, across variants too
     if ((filter_name == "text") || (filter_name == "name")) {
         handled = true;
-      std::string n(aFilter->getStringValue());
-      boost::to_lower(n);
+      const std::string n = strutils::lowercase (aFilter->getStringValue());
 
-      size_t pos = boost::to_lower_copy(name()).find(n);
+      const size_t pos = strutils::lowercase (name()).find(n);
       if (pos != std::string::npos) {
         return true;
       }
 
       for (auto var : m_props->getChildren("variant")) {
           if (var->hasChild("name")) {
-              std::string variantName(var->getStringValue("name"));
-              boost::to_lower(variantName);
+              const std::string variantName = strutils::lowercase (var->getStringValue("name"));
               size_t pos = variantName.find(n);
               if (pos != std::string::npos) {
                   return true;
@@ -146,12 +141,10 @@ bool Package::matches(const SGPropertyNode* aFilter) const
 
 bool Package::matchesDescription(const std::string &search) const
 {
-    std::string n(search);
-    boost::to_lower(n);
+    const std::string n = strutils::lowercase (search);
 
     bool localized;
-    auto d = getLocalisedString(m_props, "description", &localized);
-    boost::to_lower(d);
+    const auto d = strutils::lowercase (getLocalisedString(m_props, "description", &localized));
     if (d.find(n) != std::string::npos) {
         return true;
     }
@@ -159,7 +152,7 @@ bool Package::matchesDescription(const std::string &search) const
     // try non-localized description too, if the abovce was a localized one
     if (localized) {
         const std::string baseDesc = m_props->getStringValue("description");
-        auto pos = boost::to_lower_copy(baseDesc).find(n);
+        const auto pos = strutils::lowercase (baseDesc).find(n);
         if (pos != std::string::npos) {
             return true;
         }
@@ -167,9 +160,8 @@ bool Package::matchesDescription(const std::string &search) const
 
     // try each variant's description
     for (auto var : m_props->getChildren("variant")) {
-        auto vd = getLocalisedString(var, "description", &localized);
+        const auto vd = strutils::lowercase (getLocalisedString(var, "description", &localized));
         if (!vd.empty()) {
-            boost::to_lower(vd);
             if (vd.find(n) != std::string::npos) {
                 return true;
             }
@@ -177,8 +169,7 @@ bool Package::matchesDescription(const std::string &search) const
 
         if (localized) {
             // try non-localized variant description
-            std::string vd = var->getStringValue("description");
-            boost::to_lower(vd);
+            const std::string vd = strutils::lowercase (var->getStringValue("description"));
             if (vd.find(n) != std::string::npos) {
                 return true;
             }