diff --git a/lib/plugins/Label_2P_FM3.test.ts b/lib/plugins/Label_2P_FM3.test.ts
index 921e4bd..6e99639 100644
--- a/lib/plugins/Label_2P_FM3.test.ts
+++ b/lib/plugins/Label_2P_FM3.test.ts
@@ -88,4 +88,13 @@ describe('Label 2P Preamble FM3', () => {
     expect(decodeResult.formatted.description).toBe('Flight Report');
     expect(decodeResult.formatted.items.length).toBe(0);
   });
+
+  test('missing FM3 preamble', () => {
+    // 7 comma-parts but no `FM3 ` token in parts[0]
+    message.text = '1217,1312,+ 43.77,- 70.18, 39981, 426, 25';
+    const decodeResult = plugin.decode(message);
+
+    expect(decodeResult.decoded).toBe(false);
+    expect(decodeResult.decoder.decodeLevel).toBe('none');
+  });
 });
diff --git a/lib/plugins/Label_2P_FM3.ts b/lib/plugins/Label_2P_FM3.ts
index 0de4a86..3fceba0 100644
--- a/lib/plugins/Label_2P_FM3.ts
+++ b/lib/plugins/Label_2P_FM3.ts
@@ -23,7 +23,7 @@ export class Label_2P_FM3 extends DecoderPlugin {
 
     if (parts.length === 7) {
       const header = parts[0].split('FM3 ');
-      if (header.length == 0) {
+      if (header.length < 2) {
         // can't use preambles, as there can be info before `FM4`
         // so let's check if we want to decode it here
         ResultFormatter.unknown(decodeResult, message.text);
diff --git a/lib/plugins/Label_2P_FM4.test.ts b/lib/plugins/Label_2P_FM4.test.ts
index b6382c8..373e925 100644
--- a/lib/plugins/Label_2P_FM4.test.ts
+++ b/lib/plugins/Label_2P_FM4.test.ts
@@ -85,4 +85,14 @@ describe('Label_2P Preamble FM4', () => {
     expect(decodeResult.formatted.description).toBe('Flight Report');
     expect(decodeResult.formatted.items.length).toBe(0);
   });
+
+  test('missing FM4 preamble', () => {
+    // 10 comma-parts but no `FM4` token in parts[0]
+    message.text =
+      'KIAD,OMAA,140256,1448, 39.43,- 75.62,23228,328,  43.5, 72500';
+    const decodeResult = plugin.decode(message);
+
+    expect(decodeResult.decoded).toBe(false);
+    expect(decodeResult.decoder.decodeLevel).toBe('none');
+  });
 });
diff --git a/lib/plugins/Label_2P_FM4.ts b/lib/plugins/Label_2P_FM4.ts
index 3443d98..fd300c4 100644
--- a/lib/plugins/Label_2P_FM4.ts
+++ b/lib/plugins/Label_2P_FM4.ts
@@ -22,7 +22,7 @@ export class Label_2P_FM4 extends DecoderPlugin {
 
     if (parts.length === 10) {
       const header = parts[0].split('FM4');
-      if (header.length == 0) {
+      if (header.length < 2) {
         // can't use preambles, as there can be info before `FM4`
         // so let's check if we want to decode it here
         ResultFormatter.unknown(decodeResult, message.text);
diff --git a/lib/plugins/Label_2P_FM5.test.ts b/lib/plugins/Label_2P_FM5.test.ts
index a337dac..2cfd3d4 100644
--- a/lib/plugins/Label_2P_FM5.test.ts
+++ b/lib/plugins/Label_2P_FM5.test.ts
@@ -49,4 +49,14 @@ describe('Label_2P Preamble FM5', () => {
     expect(decodeResult.formatted.description).toBe('Flight Report');
     expect(decodeResult.formatted.items.length).toBe(0);
   });
+
+  test('missing FM5 preamble', () => {
+    // 12 comma-parts but no `FM5 ` token in parts[0]
+    message.text =
+      'EIDW,OMAA,113522,1540,+45.147, +23.384,35002,116.24,502 ,36900,ETD23N ,';
+    const decodeResult = plugin.decode(message);
+
+    expect(decodeResult.decoded).toBe(false);
+    expect(decodeResult.decoder.decodeLevel).toBe('none');
+  });
 });
diff --git a/lib/plugins/Label_2P_FM5.ts b/lib/plugins/Label_2P_FM5.ts
index a2e3125..4c169ae 100644
--- a/lib/plugins/Label_2P_FM5.ts
+++ b/lib/plugins/Label_2P_FM5.ts
@@ -22,7 +22,7 @@ export class Label_2P_FM5 extends DecoderPlugin {
 
     if (parts.length === 12) {
       const header = parts[0].split('FM5 ');
-      if (header.length == 0) {
+      if (header.length < 2) {
         // can't use preambles, as there can be info before `FM4`
         // so let's check if we want to decode it here
         ResultFormatter.unknown(decodeResult, message.text);