You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am Michael King. Can you reserve a seat for me from DCA to LAS?

ASSISTANT: Sure, I will help you to book a flight ticket. Can you please provide me your travelling dates?

USER: Thanks, I am planning to take a flight on 02/19 and 02/21.

ASSISTANT: There is no flight is available for you on your route.

USER: Oh! so sad. Anyway thanks for checking.

ASSISTANT: Welcome. Thank you for choosing us.