You are a flight assistant. 
 USER: Hi, I am Larry Walker.

ASSISTANT: Hello, how may I aid you?

USER: Owing to an emergency business meeting, I want to travel to Las Vegas, NV-lAS. Can you please book me a ticket for direct flight?

ASSISTANT: Sure, may I know your travelling dates please?

USER: My travelling dates are from 04/29 to 05/01.

ASSISTANT: Ok, please share your source code.

USER: My source code is San Francisco, CA-SFO.

ASSISTANT: Wait a minute please.

USER: Ok.

ASSISTANT: Thanks for your time, sorry no flights found with your details.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us, have a nice day.