The Kitty Hawk, after nearly five days of floating at altitudes normally used by jetliners, dropped into a Canadian meadow yesterday morning near the mouth of the St. Lawrence River, completing the first nonstop transcontinental balloon crossing of North America.

The 11-story-high helium balloon, piloted by Maxie Anderson, the Albuquerque mining company owner who rode in the first balloon to cross the Atlantic Ocean in 1978, reached speeds of up to 75 miles an hour and was nearly four miles above sea level throughout much of the flight.

"This is the toughest flight I've ever been on," Anderson, 45, said soon after he and his son Kris, 23, touched down at 7:25 a.m. in Grosse Roches, Quebec.

His balloon traveled 2,828 nonstop miles in six minutes less than 100 hours.

The Kitty Hawk, which lifted off Thursday afternoon from an Army base near San Francisco and was supposed to land nearly 1,100 miles south of the Quebec meadow in Kitty Hawk, N.C., was forced to climb over a thunderstorm in Wyoming, made a sprint from South Dakota to Maine and was saved by a Canadian military helicopter from getting entangled in spruce trees at the landing site.

"This is the first time any balloon of any type has made it from the West to the East Coast in one flight," said Brian Lawler, editor of Ballooning magazine. "This is just a feat. There is no standing record Maxie will break."

Two other balloons have attempted nonstop crossings of the United States. The first attempt last spring was stopped by a storm over Colorado. sThe second, piloted by McLean balloonist Vera Simons, crash landed in a thunderstorm last fall near Spencerville, Ohio.

Balloonist consider long-distance overland flights far more likely to be unsuccessful than flights over water because of the unpredictability of thunderstorms, which can rocket a balloon up to 100,000 feet or send it crashing to the ground.

Anderson, considered one of the world's most expert balloon pilots, outmaneuvered thunderstorms in the Rocky Mountain states by flying over one dangerous weather system and outrunning others. Helium balloons, which are notoriously difficult to steer, can only be directed by ballasting (dropping sand or water) or releasing the lighter-than-air gas, which changes the craft's altitude to take advantage of shifting winds.

Anderson kept the blue-gray Kitty Hawk headed east and northeast by flying higher than 20,000 feet all the way from northeast Utah to Maine. The balloon pilot, who said yesterday he suffered from nausea on the last two days of the flight, and his son were on oxygen through 80 percent of the unprecedented high-altitude flight.

The descent from their sub-zero temperature cruising altitude began Sunday about 10:20 p.m. when the Kitty Hawk was floating toward Presque Isle, Maine, the city where Anderson and two other balloonists launched the Double Eagle II on its record-breaking 1978 flight to France. l

But winds kept pushing the balloon north.Anderson, a millionaire who put up nearly $100,000 for the flight, attempted to put the balloon down at Loring Air Force Base in northern Maine, but again strong winds prevented the craft from descending.

"The attempt to land at Loring was one of the most tense moments of the trip. It was pitch-black and surface winds were 23 miles an hour. You couldn't see a thing," Kris Anderson recalled yesterday.

Early yesterday morning, according to Jim Mitchell, spokesman for Weather Services Corp., a Bedford, Mass., firm that specializes in balloon weather forecasting, Anderson decided to wait until dawn before attempting to land. Anderson said by radio that if he had to, he would drop the Kitty Hawk into the St. Lawrence River.

Shortly after dawn, as the Kitty Hawk hovered over the small river town of Grosse Roches, the Anderson cast out 100-foot drag ropes, which are supposed to slow the craft. The ropes tangled in 30-foot spruce trees. A helicopter circling nearby was called in to create enough wind for the Kitty Hawk to clear the trees.

"I had some of the finest help a man could have here -- unselfish, eager and competent," Anderson said after the landing.

Both Andersons, who took turns sleeping for four-hour stretches during the flight, appeared to be suffering from fatigue. Their faces were blotchy red from exposure.

Inside the balloon's gondola -- a box shaped like a six-pack of beer and made of tubular steel covered with fiberglass -- temperatures reached zero at night and shot up to nearly 70 degrees during the day. The Andersons wore several layers of woolen clothing, putting on and peeling off clothes throughout the flight.

At the landing site, the exhausted balloonists poured champagne on each other's heads. The senior Anderson said the cross-country journey was far more difficult than his transatlantic crossing because of the weather and mountains.

"We cycled from the heights of elation every day to the depths of depression," Anderson said. He added that he and his son, an engineering student at the University of New Mexico, had "met all our objectives 100 percent."

The balloonist had undertaken the flight to commemorate Wilbur and Orville Wright's turn-of-the-century aviation experiments at Kitty Hawk, N.C. Yesterday, Anderson said he was satisfied with landing in Quebec.

"I'm glad we won't have to do it again, because we made it the first time and that was tough enough," Anderson said.

In McLean, balloonist Simons, who piloted the ill-fated DaVinci Trans-America last fall, offered her congratulations to Anderson, but described his accomplishment as far different from the flight she attempted.

"Our flight was low level," Simons said. "Theirs was like a space shot. Still it was a tremendous flight." Simons, who is still recuperating from a broken leg suffered in the crash landing last October, said she is planning another low-altitude transcontinental flight this year.

As for Anderson, he has mentioned a possible balloon trip around the world. Mitchell, the meterologist who works with Anderson in planning flights, said yesterday that "Max is one of those crazy chaps who always has one or two projects in the works. We haven't heard the last of Maxie on the balloon front."