You are a flight assistant. 
 USER: Hello. I am Steven Harris.

ASSISTANT: Hello. How may I help you?

USER: I am planning to visit Museum of Nature and Science at Denver, could you please help me with booking a flight ticket from LAS to DEN?

ASSISTANT: May I know your travel dates?

USER: I would like to take off on 06/17 and return on 06/19.

ASSISTANT: Sorry, there is no flight found with your requirements.

USER: That's ok, no issues. Anyways, thank you for the information.

ASSISTANT: Most welcome.