Nursing rooms, private changing rooms, circadian lighting, pop-up shops and a 23-foot-tall wall of windows offering views of the airfield and the Bay Area are among the fresh amenities passengers will find at San Francisco International Airport when a renovated boarding area in Terminal 3 reopens Tuesday.

The $138 million makeover of 10 gates in Boarding Area E, which serves United Airlines, also includes SFO's second yoga studio, Bay Area-centric food and retail shops, furniture that includes the iconic Fritz Hansen "egg" chairs and swivel-lounge seating, and a kid's play area with an interactive art installation.

"For us it's all about enhancing the customer experience and being flier-friendly" said United spokesperson Karen May. "And these are some of the services and amenities customers have come to expect when traveling with a global carrier."

SFO's Boarding Area E project comes on the heels of the widely celebrated renovation of Terminal 2, which opened in 2011. The airport's ongoing $4.2 billion capital improvement plan also includes the reconfiguration of security checkpoints in Terminal 3 East, which should be finished by summer 2015.

SFO isn't the only airport investing in upgrades.

"We're still an industry emerging from the lingering effect of the recession, when a number of projects were put on hold," said Chris Oswald, vice president of safety and regulatory affairs at Airports Council International - North America, "but there's a more positive feeling this year than in past years and there are a number of airports actively in the midst of major, multiyear projects."

Here's a look at some of the airport upgrade projects in the works--and on the boards.

Denver International Airport is working on a $544 million project that includes a 519-room Westin Hotel and conference center and a transit center for buses and a rail line connecting the airport to downtown Denver's Union Station. The hotel and transit center are scheduled to open in fall 2015 and the new commuter rail line should begin operations in 2016.

DEN's upgrade project also includes an outdoor public plaza. "This was inspired by the plaza at the Munich Airport and to my knowledge will be the only outdoor plaza at a U.S. airport," said airport spokeswoman Julie Smith.

Dallas/Fort Worth International Airport is in the middle of a seven-year Terminal Renewal and Improvement Program, which is modernizing the original four terminals with enhanced concessions, expanded security checkpoints, reconfigured ticket counters and improved parking.

Dallas Area Rapid Transit (or DART) commuter rail will also begin serving DFW sometime this year. "The DART Orange Line will run from downtown Dallas to DFW Airport, marking the first passenger rail service to the airport," said DFW spokesman David Maga.

At $4.1 billion capital improvement program is underway at Los Angeles International Airport. The centerpiece of that project, the $1.9 billion renovation of the Tom Bradley International Terminal, opened in September 2013 and renovations are underway in Terminal 5.

In the New York area, there have been recent major upgrades in Terminal 4 at Kennedy International Airport, but the major project for the Port Authority of New York and New Jersey is a $3.6 billion replacement of LaGuardia Airport's Central Terminal Building, which first opened in 1964.

"It really is the terminal that drags down the reputation of LaGuardia and is the embodiment of how people think of the terminals at NYC-area airports in general," said Steve Sigmund, executive director of Global Gateway Alliance, a group advocating for improvements to the NYC-area airports.

In Florida, a $1.1 billion plan is just beginning at Orlando International Airport to modify and expand a wide variety of existing facilities by 2017. Upgrades include the addition of four international gates, improvements to the ticket lobby and construction of an automated people mover and rail center.

Earlier this month, design plans were released for a new North Terminal at Louis Armstrong New Orleans International Airport that will have two concourses, 30 gates, a consolidated checkpoint and a garage with 2,000 parking spaces.

The $826 million project is slated to be completed by 2018 and was described by New Orleans Mayor Mitch Landrieu as "the most transformative project for New Orleans since the Superdome." Also included will be a power plant and on-site hotel.

"Tired, dated terminals are gradually disappearing and going the way of the Dodo bird," said Mary Kirby, founder and editor of the Runway Girl Network. "In their place, passengers will increasingly find bright, sparkling new facilities bursting with concessions and, of course, an ample amount of retailers."

These changes are not only welcome for travelers, said Kirby, but also essential from a competitive standpoint.

"Airports and airlines are keenly aware that passengers are mobile, vocal and social, and it's imperative that the 'passenger experience' be considered in all terminal projects going forward," she said.

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