Forty years can be a long time to work at one thing, unless you’re doing that work in an environment that is constantly growing and changing, challenging you to keep up.Dallas/Fort Worth International Airport completed its first 40 years this week, and it’s safe to say those years have produced more growth, change and challenges than anyone could have expected.But among the airport’s leaders and the airlines that serve it, there has been no question about whether or not to keep up. In fact, four decades of effort have repaid many times the investment.It’s an over-used cliché to call DFW the engine that runs the North Texas economy, but it’s hard to imagine what that economy would be today without such an air transportation hub. It has enabled the region to take advantage of its economic strengths and geographical advantages in ways that nothing else could.It provides 60,000 direct jobs, and its economic influence provides many times that.But who’s looking back? The only good thing that can accomplish is to build confidence that the challenges of the future can be met. While maintaining and increasing its strength as a domestic hub — the largest U.S. hub for the largest airline, American Airlines after its recently completed merger with US Airways — DFW plans to capitalize on growth in international traffic.“There’ll be more consolidation around the true global superhubs and obviously, that’s where we want DFW to be — one of those successful super global hubs,” airport CEO Sean Donohue told Star-Telegram aviation writer Andrea Ahles.DFW is and intends increasingly to be a primary connecting point between Latin America, Europe and Asia.American has a strong Latin American flight network, and DFW long has been aggressive in marketing itself to other international airlines.It’s not cheap to meet these challenges — whether it be the current $2.3 billion renovation of DFW’s now-40-year-old terminals, the 2005 opening of Terminal D and the Grand Hyatt DFW, vastly improving intra-airport passenger movement with Skylink or starting plans for the next new terminal — but experience has proven the value.Happy birthday, DFW Airport.