You are a flight assistant. 
 USER: Hi, I am Daniel Lee.

ASSISTANT: Hello, how can I help you today?

USER: Can you book a flight ticket on 03/25 to attend my brother's birth day party?

ASSISTANT: Sure, kindly mention your airport codes?

USER: I want to leave from Oakland, OAK to reach Washington, IAD.

ASSISTANT: Can you please provide me your return date?

USER: I intend to return on 03/27.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Sorry to say, no flight found with your requirement.

USER: Ok, thank you.

ASSISTANT: Thanks for reaching us.