You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I want to book a flight ticket to meet my friend's who stay in CO. Can you help me to book a flight ticket?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: Thank you. July 28th and 30th are my travelling dates.

ASSISTANT: May I know your airport codes?

USER: IAD and DEN are my airport codes.

ASSISTANT: Would you like to travel in a connecting flight or a direct flight?

USER: I need a connecting flight.

ASSISTANT: May I know your good name please?

USER: Scott Smith.

ASSISTANT: Do you have any class preference?

USER: No, But I would like to travel in an normal-cost airline.

ASSISTANT: Sorry, there is no flight available on your requested dates.

USER: No issue, Thank you for the information.

ASSISTANT: You are welcome.