At a time when federal and state public works programs are stalled, the nation’s biggest airports are in the midst of major renovations or expansions that, taken together, amount to some of the largest infrastructure projects in the country.

New York’s three major airports, as well as the airports in Los Angeles, Dallas, Atlanta and Chicago, are spending billions of dollars. Many of the airports have aging terminals, some built in the 1960s and 1970s, that are ill suited to the bigger planes, bigger security lanes and bigger crowds of modern-day air travel. They are replacing or improving existing terminals, updating food concessions and parking garages, or adding runways to keep up with growing demand.

These investments are concentrated at the largest international gateways, where the growth of foreign travel has been fastest. Unlike international hub airports overseas, like Changi Airport in Singapore, Hong Kong International Airport or Frankfurt Airport, which consistently fare well in traveler surveys, airports in the United States receive low marks for customer service with more delays, more congestion and older amenities. Skytrax, a British consulting firm, found recently that six of the 10 best airports this year were in Asia, three in Europe, and one in Canada.