You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How can I aid you?

USER: I am Margaret Taylor. I am planning to attend for Music festivals in Houston, so please book a direct flight for me.

ASSISTANT: Sure, may I know your travel dates please?

USER: I will start on 09/18, return on 09/20.

ASSISTANT: Please provide your airport codes?

USER: My source and destination airport codes are DC - IAD, TX - IAH.

ASSISTANT: Thanks for your details, no flights available with your requested dates.

USER: No problem, thank you.

ASSISTANT: Thanks for opting us.