You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Kevin Walker here.

ASSISTANT: How may I assist you today? Nice to meet you Walker.

USER: My airport codes for boarding the flight are IAD to OAK. Can you book a flight ticket?

ASSISTANT: Sure. I will try to find a flight to book a ticket but I need your journey of dates to search available flight.

USER: My preferable dates for travel are 02/27 to 02/29.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: Thanks for your patience, I could not find any flight with your travel dates to book a ticket.

USER: Ok, not a problem. Thank you.

ASSISTANT: My pleasure.