diff --git a/libraries/AP_Math/crc.cpp b/libraries/AP_Math/crc.cpp
index 24e1135313..ab0ec7be0e 100644
--- a/libraries/AP_Math/crc.cpp
+++ b/libraries/AP_Math/crc.cpp
@@ -339,6 +339,14 @@ uint16_t crc16_ccitt(const uint8_t *buf, uint32_t len, uint16_t crc)
     return crc;
 }
 
+uint16_t crc16_ccitt_GDL90(const uint8_t *buf, uint32_t len, uint16_t crc)
+{
+    for (uint32_t i = 0; i < len; i++) {
+        crc = crc16tab[crc >> 8] ^ (crc << 8) ^ (uint16_t) *buf++;
+    }
+    return crc;
+}
+
 /**
  * Calculate Modbus CRC16 for array of bytes
  * 
diff --git a/libraries/AP_Math/crc.h b/libraries/AP_Math/crc.h
index 276f73b469..bb369302f6 100644
--- a/libraries/AP_Math/crc.h
+++ b/libraries/AP_Math/crc.h
@@ -37,6 +37,10 @@ uint8_t crc_sum8(const uint8_t *p, uint8_t len);
 // Contact: Fergus Noble <fergus@swift-nav.com>
 uint16_t crc16_ccitt(const uint8_t *buf, uint32_t len, uint16_t crc);
 
+// CRC16_CCITT algorithm using the GDL90 parser method which is non-standard
+// https://www.faa.gov/nextgen/programs/adsb/archival/media/gdl90_public_icd_reva.pdf
+uint16_t crc16_ccitt_GDL90(const uint8_t *buf, uint32_t len, uint16_t crc);
+
 uint16_t calc_crc_modbus(uint8_t *buf, uint16_t len);
 
 // generate 64bit FNV1a hash from buffer