Google has launched a new flight search tool. At the moment it is only offering a limited number of cities but they plan to add more functionality in the future.
Article on The Washington Post:
http://wapo.st/qRWTNe
I looks like a very useful tool when researching flights for your clients. On a personal level, I love the feature that allows you to enter a price and flight duration, and based on your departure point it will give you all the flight options available for your criteria.
Another great service from Google!
Here's the link to the actual tool:
http://www.google.com/flights/