The 2.1 percent increase came as airport officials launched a $100 million renovation designed to streamline security check-ins, eliminate a major passenger bottleneck and give Southwest Airlines, the airport's No. 1 carrier, room to grow.
"The airport is an important transportation and economic resource that supports 21,000 jobs," Gov. Martin O'Malley said in a statement. "This record year is another sign of Maryland's strong recovery from the national economic downturn."
With 56 percent of BWI's passenger business, Southwest served more than 12.5 million passengers last year, a 7 percent increase over 2010. The airline added flights to Newark, N.J., and South Carolina last year.
Meanwhile, AirTran Airways, BWI's No. 2 carrier — which is merging with Southwest in a $1 billion deal — added flights to Bermuda and Aruba and increased service to Cancun and Montego Bay.
Earlier this week, the U.S. Department of Transportation announced that 91 percent of arrivals at BWI and 88.4 percent of departures were on time in December.
In April, Southwest is to receive new, larger aircraft, the Boeing 737-800, with BWI among the first airports to get them. The initial flights will be to and from Florida, a company spokeswoman said. After that, Southwest will use the planes on its BWI-to-California routes.
Over the course of a two-year renovation approved in December by the state Board of Public Works, BWI is to expand the number of security lanes on Concourse C from six to nine and to create space to accommodate the newest security technology.
The renovation will also allow passengers to move among the 26 gates at Concourses A and B and the 14 gates at Concourse C without passing through security a second time. In addition, Concourse C will be given the level of amenities found at the A and B concourses, from new concessions to upgraded waiting areas.
The airport will pay for the project with revenue from gate leases, landing fees, parking fees, rents from vendors and advertising.
Initial construction is expected to be completed before the Thanksgiving travel period this year; the rest is to be finished before the summer travel season in 2013.