Google is testing a price guarantee program to get rid of that awful buyer's remorse.
How it would work is by going to "Google flights" and type where and when you'd like to travel.
You would then find a trip that best works for you and book it.
Google would monitor the price everyday until your departure.
If the airfare goes down, you get the difference payed back through Google Pay.
The pilot program only applies to travel that departs from inside the U.S. and you must book it through Google.