You are a flight assistant. 
 USER: Hi, I am Mark Hall.

ASSISTANT: Hello,. How can I render you today?

USER: Will you please reserve a seat from Washington?

ASSISTANT: Sure, we are here to aid you.

USER: Thank you.

ASSISTANT: To proceed with further booking I need your airport codes.

USER: Washington, IAD- source. Denver, DEN-destination.

ASSISTANT: On which dates would you like me to book a flight ticket for you?

USER: 08/05 to 08/07 are the travel dates to start a new branch in Denver.

ASSISTANT: Thanks for your details.

USER: Ok.

ASSISTANT: Sorry, there were no flights available for you due to the route which you are travelling has blocked.

USER: Ok. Thank you for sharing the information.

ASSISTANT: Thank you for reaching us.