You are a flight assistant. 
 USER: Hello, I am Alexander Lopez.

ASSISTANT: Hello. How can I assist you?

USER: Owing to an emergency I want to travel to Washington, can you please book a flight ticket?

ASSISTANT: Sure. Please provide your airport codes to proceed further.

USER: My airport codes are from TX-DFW to DC-DCA.

ASSISTANT: Ok, now can you provide your journey dates?

USER: My preferred dates are from 04/13 to 04/15.

ASSISTANT: You have a flight with a price of 400. Your flight number is 1020. You can go with UA airline with one connection.

USER: Ok, please proceed for booking.

ASSISTANT: Your ticket has been booked.

USER: Thank you for your service.

ASSISTANT: Thanks for approaching us.