"Alexa, book me a flight to Sydney for Wednesday"
Alexa knows that I'm in Melbourne, that I always fly economy class on flights under three hours, have a strong preference for Oneworld airlines, fly direct whenever possible, and like to fly in the mornings except between 8am or 10am on weekdays.
"I found three flights on Wednesday that match your preferences. On your kitchen screen now. Which one shall I book?"
The next development after that would be intermodal transport scheduling and calendar awareness: "Alexa, book me travel for the Sydney board meeting". "Here's an itinerary that matches your diary and preferences."