The $2.3 billion renovation of Dallas/Fort Worth Airport’s four oldest terminals will run over-budget, the airport board’s operations committee was told Tuesday.That’s not something to dismiss lightly, but neither is it a reason to panic. The real bottom line is that the bulk of the renovations must move forward.It’s important to remember that the airport, which opened in 1974, is not financed with tax money. It pays its bills with a combination of airline landing fees, terminal rents, parking revenue, concession revenue, car rental fees, facility leases and other operating income. It makes facility improvements through bond sales financed by other fees, along with federal grants.The airport has committed $1.25 billion so far to contracts connected with the seven-year renovation program for Terminals A, B, C, and E.Board member Bernice Washington told the operations committee Tuesday to expect “substantial overruns” on the project. She did not give a figure, but substantial is not a word you want to hear linked to overruns on something that’s already expected to cost $2.3 billion.More details are expected to come in a report to the full 12-member airport board in September.Washington cited increased building material costs, a greater-than-expected need for asbestos removal in Terminal B, and delays associated with the bankruptcy of American Airlines and its pending merger with US Airways.Certainly, the full board will want to scrub through the project list again to look for appropriate savings. But board members also must acknowledge that an airport lives or dies according to the experiences airline passengers have there. These terminals are so old that their impact on passengers’ experience at DFW is not good.Beginning in October 2014, DFW will face full, unrestricted competition from Dallas Love Field, which by that time will be completing its own renovation and expansion program.DFW will still be the region’s airport for international travel, but it’s important to remember that international flights and passengers have many alternatives as far as U.S. destinations and connections. Cost overruns at DFW will undoubtedly be expensive, but the airport cannot afford to lose its advantages because of old, worn-out terminals.