Small planes can fly again over the nation's tallest building. Picnics are back along the Mississippi River. But visitors still must pass through metal detectors to reach Liberty Island, home of the Statue of Liberty.

Seven months after the nation tightened security in response to the terrorist attacks, some measures have been quietly dropped, while others have been woven into the fabric of a new, more cautious life in the United States.

Fewer soldiers are stationed at airports and state capitols, but the long lines of travelers, extra metal detectors and bag searches remain. Parking restrictions have been lifted at some government buildings, but the temporary concrete barriers set up around them after Sept. 11 have been replaced by enormous, permanent planters.

The American public seems to have changed, too. People who initially bristled at the inconvenience and intrusiveness of personal searches now accept them as part of the daily routine as they enter their workplaces.

When Justin Stein, a security guard at the Chicago Mercantile Exchange Center, began searching bags and briefcases last fall, people expressed annoyance and some even left the building in protest.

But as the weeks went on, he said, "they started to acknowledge our efforts, and people started realizing it could easily have been us that were killed."

Across the country, many officials have refined their approaches to security since their initial, all-out response to the attacks.

"We now are moving from that kind of knee-jerk phase," said Daniel Goure, an intelligence and defense expert at the Lexington Institute in Washington. "This is a much more complex or subtle problem than the way we treated everything at first, which was just protect everything and put barriers around everything."

The FBI has eased off issuing "high alerts" for the nation but has begun giving more specific information. Last week, the FBI warned of possible attacks on targets such as banks, shopping centers and supermarkets.

At the federal courthouse on Worth Street in New York City, less than a mile from the site of the World Trade Center, federal marshals carrying shotguns no longer stand guard at curbside. But a tent has been installed outside the entrance to provide the first of two security checkpoints.

The Federal Aviation Administration has lifted various flight restrictions over Washington, New York City and Boston. In Chicago, officials expressed concern earlier this month when the FAA ended the no-fly-zone for small aircraft that had been in place over the downtown area, including the Sears Tower, the nation's tallest building. The officials have not decided whether to ask the FAA to reconsider.

Some of the last flight restrictions were lifted at Reagan National Airport on Saturday. The restrictions had been imposed because of the airport's proximity to important government buildings, including the Pentagon. There are still some special rules in effect, including the no-standing rule on all planes within 30 minutes of takeoff and landing, and the use of passwords by pilots when landing.

The government has begun relaxing other post-Sept. 11 rules, such as parking bans at airports. At Chicago's O'Hare Airport, drivers may again park in garage spaces that are within 300 feet of the terminal.

The posting of National Guardsmen at airports, one of the most visible reactions to the terrorist attacks, has all but ended. The soldiers are being replaced by local law enforcement officers until the federal government's own officers are hired, trained and in place.

Several states have begun to scale back troops called up for other duty. For instance, in Iowa, officials have reduced the number of soldiers deployed to military bases and other sites from 900 to 650.

National Guard patrols at state capitols and nuclear reactors are also getting smaller. And law enforcement officers who were working extra shifts have significantly reduced patrols at shopping centers and recreational areas.

"If you go full-blow, it's very expensive," said Norm Arnold of the Alabama National Guard. "The manpower was one of the big things."

Along the Mississippi River, the Army Corps of Engineers has reopened some picnic and observation areas near key locks and dams. But commercial traffic remains banned on the road that winds through the Hoover Dam on the Arizona-Nevada line.

In Idaho, Gov. Dirk Kempthorne was criticized for imposing measures so severe that the Capitol was nicknamed "Fort Kempthorne." Most of those restrictions have since been lifted. The governor had ordered, for instance, that streets near the Capitol be blocked off, that concrete barriers be erected and that all but two entrances be closed.

Elsewhere around the country, NASA has stopped announced launch times at Cape Canaveral, Fla., until 24 hours before liftoff.

The White House, which was closed to the public after Sept. 11, has started allowing tours again, but only for school groups that make arrangements beforehand. The FBI and Pentagon are doing the same thing.

"A good homeland security system should be nearly invisible to the average citizen because it isn't going to be the cop on the beat, per se, or the National Guard," said Goure, the security analyst. "It's likely to be some computer jock who's cross-referencing data or some camera that can do visual identifications. Proper, good security should be invisible."