Google Flights will pay you the difference if a ticket gets cheaper after you book — here's how to use the new tool

• Google Flights launched a "price guarantee" program for some flights departing from the US. 
• If you buy an eligible ticket and the price drops afterward, Google will pay you the difference.
• The airfare rebate program is capped at $500 a year. Here's how it works.

There's a million things to be anxious about while flying — but Google wants overpaying for your ticket to be scratched off the list.