You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am Michael Martin, I want to book a flight ticket on 08/26 and return ticket on 08/28. Can you help me to book a flight under fare of 1000?

ASSISTANT: Sure, can you please help me with your airport codes?

USER: I will fly from PA-PHL to DC-DCA.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say, no flights found with your requirement.

USER: Ok, thank you for the information.

ASSISTANT: Thanks for reaching us, have a good day.