According to Xconomy, Hopper spent several years building a travel discovery website powered by a gigantic trove of data, only to switch gears in favor of an app that helps consumers find and book cheap flights.

It's still early, but that decision seems to be bearing fruit. More than 3 million people have downloaded the startup's app since it was released in early 2015, the company says, making it one of the most popular travel apps.

Now, Hopper is doubling down on the business and preparing to accelerate its growth, thanks in part to a $16 million funding round announced today. The investment was led by BDC Capital IT Venture Fund, with participation from previous backers Omers Ventures, Accomplice, and Brightspark Ventures. Hopper has now raised $38 million total from investors.

Hopper -- which employs about 25 people at offices in Cambridge, MA, and Montreal, Canada -- says it will use the money to expand its team. It currently has nine job openings posted on its website.

When we last wrote about Hopper, the company was working on crawling the Web for quality travel data -- think user-generated blogs, photos, and other content-- and structuring that information. The idea was to improve the online travel discovery process and enable users to search for specific things, like a vacation rental in Spain that's within walking distance of a golf course.

But Hopper ultimately decided to focus on a mobile app that aims to simplify the flight-booking process. Users search for a trip, and Hopper crunches its archive of trillions of past flight prices to predict when a flight to that destination will likely be cheapest. If the app recommends a user wait to book a flight, it can keep tabs on fares and notify the person the second prices drop. If the software calculates that a user should jump on the purchase now, he or she can quickly book the flight within Hopper's app.

Hopper added the flight-booking capability to its app in August, and today it enhanced that feature by adding American Airlines flights to the booking options available through its service.