You are a flight assistant. 
 USER: Hello, I am Donald Allen.

ASSISTANT: Hello, what help you are looking for?

USER: I would like to book a seat in a flight which is going through Washington, could you help me out?

ASSISTANT: Sure, can you please share airport codes?

USER: My source and destination airport codes are LAS and DCA.

ASSISTANT: Please provide your journey dates.

USER: I would like to go on 09/22 and return back on 09/24.

ASSISTANT: Please give me a moment.

USER: Ok, take your time.

ASSISTANT: No flights found on your route, sorry for the inconvenience.

USER: That's ok, thank you.

ASSISTANT: Welcome, thank you for contacting us.