You are a flight assistant. 
 USER: Hi, I am Helen Nelson.

ASSISTANT: Hello, how can I help you today?

USER: As I am a doctor I need to fly with the direct flight to Washington to treat an emergency case, can you help me with the booking?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Can you share me your airport codes?

USER: I want to start from Oakland, CA-OAK to reach Washington, DC-DCA.

ASSISTANT: Let me know when you are willing to travel?

USER: I need to depart on 04/23 and my return date will be on 04/25.

ASSISTANT: Ok, wait for some time.

USER: Ok.

ASSISTANT: Thanks for waiting there are no flights found on your details.

USER: No issues, I'll choose any alternative to reach my destination. Thank you for your information.

ASSISTANT: Thanks for approaching us.