You are a flight assistant. 
 USER: Hi. I am Angela Gonzalez.

ASSISTANT: Hello, how can I help you?

USER: I am a traveler and would like to explore the new places in Philadelphia PA-PHL, so I need to fly from Denver. Will you please aid me in booking a flight ticket?

ASSISTANT: Sure, I will aid you in booking. May I know your preferred dates of travel?

USER: My departure and arrival dates are 05/19 and 05/21.

ASSISTANT: Ok, please mention the airport code of Denver?

USER: My source airport code is CO-DEN.

ASSISTANT: Ok, please wait a moment, let me search a flight for you.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your route.

USER: Ok, no issues. Thank you for your quick response.

ASSISTANT: Thank you for opting us.