You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, welcome to flight booking agency. How can I guide you for today?

USER: Rachel Clark here. I would like to visit Houston to attend a birthday function so please help me with flight ticket booking from Washington DC.

ASSISTANT: Sure, can you please provide your nearest airport codes?

USER: Sure, I have planned to travel from IAD to HOU.

ASSISTANT: Could you please help me with your preferable journey dates?

USER: Sure, I would like to travel on dates of 02/17 and 02/19.

ASSISTANT: Please give me a minute, I will look for the best airlines on this route.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no flight available on your requested dates.

USER: Oh! It is sad to hear. Anyway, thank you for checking.

ASSISTANT: Thank you for availing us.

USER: Most welcome.