Mobile apps and Web sites are helping to change the way people book their travel. As some discount bookings sites discovered last year, untethering travel commerce from the desktop or laptop frees the consumer to book sometimes on a moment’s notice. And as mobile users gain confidence in m-commerce systems, they are willing to research and buy full travel itineraries.

The latest estimates and projections from eMarketer suggest that mobility is a key growth driver in an online travel category that is otherwise approaching maturity.

eMarketer says that in 2011, 12.1 people in the U.S. booked travel on their phones --  a number that will shoot up to 16 million this year, grow to 20.2 million next year and hit 36.7 million in 2016. Perhaps just as important is the even larger role mobile platforms will play in the longer research and purchase process.