Judge Margot Botsford's ruling appeared to end a long and contentious battle between Massport and several municipalities, including Boston, that had argued that a fifth runway would further burden residents who have long put up with thundering noise and the stench of jet fuel.
Massport officials, noting that Logan has some of the worst flight delays in the nation, revived plans for the runway in 1995. They insisted that the airport needed a 5,000-foot, northwest-southeast runway to help contend with northwest winds, which can force the temporary closing of up to three of the airport's four runways, cutting takeoffs and landings by more than 50 percent. It is safest for planes to land and take off into the wind.
Opponents wouldn't say yesterday whether they plan to appeal the decision, and Mayor Thomas M. Menino, the strongest critic of the runway, said it seemed time to move on.
"I'm disappointed, but right now it looks like I'll accept the decision," Menino said. "There was a time I'd say `continue to fight,' but we've fought this thing . . ."
While Logan aviation director Thomas J. Kinton Jr. said construction would begin next spring and take about two years, there appeared to be at least two legal hurdles remaining.
A suit filed in federal court by opponents, including Communities Against Runway Expansion and South Shore Jet Pollution Council, challenges the Federal Aviation Administration's approval of the runway. The groups say the FAA did not adequately analyze the noise effects and the impact on the air quality of their communities. Arguments in that case are scheduled to begin Monday at the US Court of Appeals in Washington, D.C. The suit challenges the FAA ruling that says the runway can be used only when winds from the northwest or southeast exceed 10 knots per hour, the equivalent of 11.5 miles per hour. The community groups are seeking a higher threshold.
Kinton, however, said "we certainly will go forward" with construction, even if that appeal and another South Shore lawsuit are unresolved.
"We think this will remedy a longstanding structural deficiency of our airfield when the winds are strong from the northwest," he said. "This will cut the delay problem by some 30 percent in total. It does not cure the delay problem at the airport, but it fixes the thing we can do something about."
US Representative Michael E. Capuano, a Democrat representing Boston, Cambridge, Chelsea, and Somerville, hadn't read the decision and said that while he trusts Menino's lawyers have given him wise counsel, "there still seem to be many more battles ahead."
William Manning, a representative of Communities Against Runway Expansion, based in East Boston, said yesterday's decision was disappointing, and called Massport's proposal a betrayal of earlier promises made to neighbors in the 1970s. "They are just trying to jam more concrete into East Boston," he said. "It's an obvious example of Massport violating its agreement with the community."
The injunction, granted in 1974 at the request of Boston's mayor, Kevin H. White, barred Massport from any expansion of the airport. As air travel increased dramatically in the 1990s, Massport set out to overturn the injunction, arguing that the circumstances that might have prompted it no longer existed.
In yesterday's ruling, Botsford noted that the original injunction was not a permanent contract and "was subject to modification" when fairness dictated. Botsford acknowledged the flight delays that have plagued Logan in recent years, and noted that when the original injunction was issued, "it appears undisputed that Logan Airport was not experiencing any meaningful level of delay."
But the 1980s, she wrote, brought increases in passenger traffic, and by 2000 the airport had a record high 27.7 million passengers. "Not even Nostradamus could be expected to envision what air traffic demand would look like this far in the future," Botsford wrote.
While noting that the number of passengers has since dropped at the airport, she agreed with Massport officials who called the downturn a "blip" because of the lingering effects of a poor economy and decreased flight demand following the terrorist attacks of Sept. 11, 2001.
At Logan, flight delays increase when moderate northwest winds blow, forcing the airport to close two of its four runways and dropping the airport's maximum capacity from 120 arrivals and departures per hour to 90. When the northwest winds are strong, three runways are closed and the number of arrivals and departures drops to 60 per hour.
Because of its relatively short length, the proposed 5,000-foot runway would be usable only by turbo-prop planes and small jets. But the use of such jets at Logan is growing rapidly -- it doubled to 20 percent of all flights in 2001 -- and the FAA has said that runway-related delays in 1998 could have been reduced by about one-third if the new runway had been in place.
Botsford also acknowledged "eloquent trial testimony" from nearby residents about the potential noise impact, but concluded the runway would reduce the number of people exposed to the highest levels of noise -- at or above 75 decibels -- even while it would increase the number exposed to levels lower than 65 decibels.
She also concluded that Massport's plan to cap smog-related chemicals at 1999 levels offered assurances that the runway would not result in an increase in noxious emissions. And she rejected an alternative proposal to shift traffic to Hanscom Field in Boston's western suburbs, saying any increase in traffic there would be up to carriers.
A traveler at Logan yesterday endorsed the runway plan.
"I know the people around here don't want any more noise, but there are big delays to deal with," said Katie Serio of Medford. "Boston is very, very busy. So this may be progress."
Globe correspondent Sasha Talcott contributed to this report. Material from the Associated Press also was used.
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