diff --git a/python/fusion_engine_client/messages/control.py b/python/fusion_engine_client/messages/control.py
index 08fa3401..522a58fc 100644
--- a/python/fusion_engine_client/messages/control.py
+++ b/python/fusion_engine_client/messages/control.py
@@ -641,6 +641,11 @@ class ShutdownRequest(MessagePayload):
     MESSAGE_TYPE = MessageType.SHUTDOWN_REQUEST
     MESSAGE_VERSION = 0
 
+    ## Stop navigation engine if running and flush calibration to non-volatile storage.
+    STOP_ENGINE = 0x0000000000000001
+    ## If a log is being generated, end that log.
+    STOP_CURRENT_LOG = 0x0000000000000002
+
     ShutdownRequestConstruct = Struct(
         "shutdown_flags" / Int64ul,
         Padding(8),
@@ -678,6 +683,11 @@ class StartupRequest(MessagePayload):
     MESSAGE_TYPE = MessageType.STARTUP_REQUEST
     MESSAGE_VERSION = 0
 
+    ## Start navigation engine if not running.
+    START_ENGINE = 0x0000000000000001
+    ## If a log is not being generated, start a new log.
+    START_NEW_LOG = 0x0000000000000002
+
     StartupRequestConstruct = Struct(
         "startup_flags" / Int64ul,
         Padding(8),
diff --git a/src/point_one/fusion_engine/messages/control.h b/src/point_one/fusion_engine/messages/control.h
index bf515f52..285b955d 100644
--- a/src/point_one/fusion_engine/messages/control.h
+++ b/src/point_one/fusion_engine/messages/control.h
@@ -570,7 +570,23 @@ struct P1_ALIGNAS(4) EventNotificationMessage : public MessagePayload {
 struct P1_ALIGNAS(4) ShutdownRequest : public MessagePayload {
   static constexpr MessageType MESSAGE_TYPE = MessageType::SHUTDOWN_REQUEST;
   static constexpr uint8_t MESSAGE_VERSION = 0;
-  /** A bitmask of flags associated with the event. */
+
+  /**
+   * Stop navigation engine if running and flush calibration to non-volatile
+   * storage.
+   */
+  static constexpr uint64_t STOP_ENGINE = 0x0000000000000001;
+  /**
+   * If a log is being generated, end that log.
+   */
+  static constexpr uint64_t STOP_CURRENT_LOG = 0x0000000000000002;
+
+  /**
+   * A bitmask of flags associated with the event.
+   *
+   * @note For backwards compatibility, a value of `0` is treated as if the
+   *       STOP_ENGINE bit is set (`0x0000000000000001`).
+   */
   uint64_t shutdown_flags = 0;
   uint8_t reserved1[8] = {0};
 };
@@ -587,7 +603,22 @@ struct P1_ALIGNAS(4) ShutdownRequest : public MessagePayload {
 struct P1_ALIGNAS(4) StartupRequest : public MessagePayload {
   static constexpr MessageType MESSAGE_TYPE = MessageType::STARTUP_REQUEST;
   static constexpr uint8_t MESSAGE_VERSION = 0;
-  /** A bitmask of flags associated with the event. */
+
+  /**
+   * Start navigation engine if not running.
+   */
+  static constexpr uint64_t START_ENGINE = 0x0000000000000001;
+  /**
+   *  If a log is not being generated, start a new log.
+   */
+  static constexpr uint64_t START_NEW_LOG = 0x0000000000000002;
+
+  /**
+   * A bitmask of flags associated with the event.
+   *
+   * @note For backwards compatibility, a value of `0` is treated as if the
+   *       STOP_ENGINE bit is set (`0x0000000000000001`).
+   */
   uint64_t startup_flags = 0;
   uint8_t reserved1[8] = {0};
 };