THE SERIES Part 1: The big gamble Part 2: Making the decision Part 3: Designing the 757 Part 4: Pulling it together Part 5: Will it really fly? Part 6: An act of faith Part 7: The delivery Part 8: The quest for simplicity

During a 2 1/2-mile drive skirting the edge of Miami's international airport, Frank Borman and Tex Boullioun agreed to an enormous gamble.

Borman, president of Eastern Airlines, and Boullioun, then president of Boeing's commercial airplane division, knew the gravity of the decision they were making. But it wasn't apparent from their casual, confident manner during the four-minute automobile ride on a sun-drenched August Day in 1978.

Boeing and Eastern had talked for much of 1977 and 1978 about a new airplane, one on which both Borman and Boullioun would risk the futures of their companies.

They had some ideas. The airplane would be a much0updated derivative of the popular single-aisle Boeing 727, with two engines instead of three. It would have about 160 seats. Eastern and British Airways together would launch the airplane, giving Boeing the sales orders and cash to begin production.

Then, on that August morning in Miami, Borman surprised Boullioun and other Boeing executives who had gathered at Eastern's headquarters at the edge of the airport. Borman asked to see data on a hypothetical plane about 15 seats bigger than they'd talked about earlier.

Boeing officials, though not eager to increase the size of the plane, obliged and laid out the material for Borman, who was noncommittal. Boullioun had to leave early, and Borman said he'd see him to the airport terminal.

Once together in the back seat of the car, Borman told Boullioun he liked the bigger airplane design and was willing to gamble on it.

All at once Borman had a flash that a 175-passenger airplane was what Eastern wanted," Boullioun recalled. "He said, 'If you'll build that, we'll go.'"

Boullioun replied: "You've got it."

And so, with a handshake-just as the car jiggled over some railroad racks-the Boeing 757 was born.

"It was a recognition of months and months of negotiation," Borman recalled recently. "Finally we had an accommodation. We knew we were going to be able to do it. They laid out just the airplane we wanted."

Launching a commercial airplane project sobers an airline because it must hazard millions of dollars on a plane that won't fly for years.

But an airline's risks pale next to those of an airplane manufacturer, which may spend $1.5 billion or more on a new design. Not many new aircraft are launched, because a sales flop literally can drive a manufacturer out of the commercial airplane business, as Lockheed proved with its L-1011 jetliner.

"It's the world's biggest poker game. The risks are fantastic," said Ken Holtby, a top Boeing vice president. "We bet the company over and over again in terms of our net worth."

Today the 757 is in service with both Eastern Airlines and British Airways and is proving claims that it would be the world's most fuel-efficient airplane.

But bringing together the elements to make a new idea fly is an immensely detailed process. In the case of the 757, it began well before Borman and Boullioun shook hands, and still isn't finished.

"Sometimes I sit back in amazement and look up at an airplane flying overhead," said Malcolm Stamper, president of the parent Boeing Co. "It's flying people at these tremendous speeds over long distances. And, you think, it was just a bunch of parts, pieces of paper on the ground.

"I think when you build an airplane for the first time it's an excitement because it didn't exist. Take the 757. Somebody said, "We'll cut out this piece of sheet metal and we'll bend it this way. And we'll go get this wire and we'll string it this way. And this pipe and bend it.'

"And they put all these things together and they're inanimate. Nothing's moving. Then they fill it up with fuel, light it up, and it takes off and flies! It becomes alive all of a sudden."

Part 1: The big gamble