POST being sent as a GET
<mx:HTTPService id="userRequest" url="url"
                useProxy="false" method="POST" result="checkTransmissionCode()">
    <s:request xmlns="">
        <transmissionCode>{transmissionCode_TextInput.text}</transmissionCode>
    </s:request>
</mx:HTTPService>

private function sendCode() :void{
     userRequest.send();
}

private function checkTransmissionCode() :void {
            if(userRequest.lastResult.authorization=="correct"){
                this.currentState='transmission';
            }
            else{
                Alert.show("Invalid");
            }
            userRequest.clearResult();
        }

private function sendCode() :void{
 userRequest.headers['X-HTTP-Method-Override'] = 'POST';
 userRequest.send();
}