Riding on the back of a 747 jet, the space shuttle Enterprise wowed and wondered hundreds of thousands of Washingtonians yesterday as it flew low and ceremoniously around the Capital Beltway, up the Potomac and out to a brass-band welcome at Dulles International Airport.

People clutching binoculars, picnic baskets and newborn babies gathered in parking lots, vacant fields, along highways and on the steaming concrete apron at Dulles to see the delta-winged spacecraft, which was making its first visit to Washington.

Cruising at about 250 mph as low as 1,200 feet, the shuttle drew applause, whoops, gasps and declarations of awe as it came into view over trees and between buildings, moving against a bright summer haze.

"I wish I were that pilot. Everyone wishes he were that pilot," said James L. Strayer, as the plane passed the Edsall Road interchange on I-395, near the Beltway. Strayer said he had rushed down to Washington after leaving his job in Johnston, Pa., at 1 a.m. yesterday morning to see the shuttle and to visit his son in Annandale.

"It's neat," said 9-year-old Leah Osteen of Silver Spring as she studied the spacecraft through a pair of binoculars at Dulles. She was part of a crowd estimated at between 50,000 and 100,000 that was on hand when the piggy-back craft touched down with a cloud of tire smoke at 10:37 a.m.

The Enterprise and its transport jet remained on display throughout the afternoon at Dulles, drawing tens of thousands more people despite soaring temperatures. This morning they are scheduled to take off for Edwards Air Force Base in California.

The shuttle drew oohs and ahs in countless variations during the day.

"It's terrific. It gives me chills just to look at it," said federal employe Margarita Labrada, after the Enterprise passed over the Beltway's Connecticut Avenue interchange to the delight of several hundred people who had gathered near the Mormon Temple, many of them parking illegally.

"It's worth every penny even if it does nothing but raise the morale of the country," remarked Sharon Hamon at Dulles. She said she had come from Atlanta to see the shuttle and to visit relatives.

The Enterprise, the first shuttle off the assembly line, has been used in glide tests but has not flown in space. It has no engine and lacks the support systems needed for orbital missions.

Its visit to Washington was the final leg of a 16,000-mile public relations tour that took it to France for the Paris Air Show, five other European countries, Canada and St. Louis and over the skyscrapers of Manhattan.

The National Aeronautics and Space Administration brought it to Washington, NASA spokesman James Kukowski said, because of interest in Congress and various government agencies and to "show anyone who was interested in the program that it's working."

The shuttle and its 747, a former American Airlines jetliner equipped with special high-powered engines, took off from Scott Air Force Base near St. Louis at 7:15 a.m. Washington time yesterday morning, and arrived over the Baltimore area at about 9:15 a.m., where it circled the city over I-695 at about 2,000 feet, watched by countless spectactors below.

Running a few minutes ahead of schedule, the crew decided to divert to an air show at Easton, Md. Then, the two craft approached Washington up the Potomac, turning right at the Woodrow Wilson Bridge for a 360-degree circuit of the Beltway.

Spectators, many of them tuned in to radio stations that tracked the shuttle's progress, staked out open space well in advance. WTOP radio traffic monitor Bob Marbourg estimated 50 to 75 cars were pulled over at each beltway interchange. "Both sides of Kenilworth Avenue were lined about a quarter mile inside, quarter mile outside the beltway," Marbourg said.

Turning up the Potomac from the Wilson bridge, the lumbering craft dropped to 1,200 feet to give people a better view.

The driver of a Metrobus moving through Alexandria toward National Airport was so excited to see it flying up the river that she jumped out and ran to the rear for a better look. Two passengers slipped aboard while she was watching, but made good on their fares when she returned.

As the craft flew past the Washington Monument, tourists pointed upward en masse and fumbled with camera settings. Schoolchildren piled out of buses parked on 17th Street NW and shouted "There's the space ship, just like on TV!"

An 11,500-foot-long runway at Dulles was closed down and turned over to parking, and people began gathering there at about 7 a.m. Shuttle pins and styrofoam replicas went on sale in the airport gift shop and NASA passed out 40,000 tiny American flags and shuttle lapel buttons.

The concrete apron in front of the terminal became a giant picnic ground, with lawn chairs, radios, ice coolers and flying Frizbees in plentiful supply. Traffic was sluggish, but paralyzing jams that were predicted did not materialize.

The crowd murmured with excitement as the two planes appeared moving slowly across the north sky. Adults whooped and children screamed, some of them being hoisted onto shoulders for a better view.

The pilots lined up on a north-south runway, dropped to 30 feet from the surface, then pulled back on the throttles and took the craft climbing back up, a maneuver frequently employed to give crowds an extra thrill. After circling again, it touched down. After the 747 taxied to a fenced-off area in front of the terminal, a crew member opened its door and unfurled a large American flag in the bright sun, drawing fierce applause. The U.S. Air Force band struck up "Stars and Stripes Forever".

A British Airways supersonic Concorde jet bound for London took off and flew a low-level salute over the shuttle, its tail low in the air, and its engines delivering a sonic boom that drowned out all other noise.

Arlene Sweeney of Chantilly turned to a stranger and declared: "That's the most beautiful thing I've ever seen."

The shuttle was parked through the afternoon. People pressed up against the fence, speculated about heat-resistant tiles and posed for photos with the spacecraft as backdrop. Small children pestered parents about why they couldn't go aboard, while older children such as 12-year-old Amy Larsen of Winchester, Va., discoursed to them about technology and techniques of the space program.

"I think it's really neat and I'm going to ride it when I grow up," said 8-year-old Misha Malik of Centreville.