You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How shall I help you?

USER: I am Robert Hill, I want to book a direct flight from Houston, help me in booking my flight ticket .

ASSISTANT: Please provide your travel dates?

USER: 02/12 to 02/14 are my travelling dates.

ASSISTANT: Could you please provide airport codes?

USER: My source point is Houston TX-HOU, my landing point is at Washington DC-IAD.

ASSISTANT: No flights found.

USER: No problem, thank you.

ASSISTANT: Thanks.