It's the biggest building in the world - ''in cubic footage as we know it,'' the guide adds somewhat cryptically. It's where the Boeing Commercial Airplane Company makes 747s and 767s. The big doors through which the finished planes roll are as high as a football field is wide, and as broad as a field is long. You don't walk through this plant, you drive through it.
But it is definitely a building - what you might call an indoors situation - and this is recognizably an assembly line, however enormous. To drive past a couple of 747 aircraft in process in this interior setting, with workers scurrying around them, is to be overwhelmed by the sheer size of the planes in a way that doesn't happen at an airport.
To the casual observer unschooled in aerodynamics, it is nothing less than amazing that such a huge craft can take flight.
It is no less amazing that the commercial aircraft industry itself remains airborne.
To look around the industry is to see lots of reasons not to be in it. This is the industry that gave to our language the phrase ''the learning curve.'' New-product development costs are such that usually no company can build a new airplane alone. It is a group effort. To launch a new aircraft is ''to bet the worth of the company.''
Aircraft manufacturers, who subsidize their commercial activities with the (controlled) profits from their military sales, have to settle for margins on their commercial projects that would be scorned by the produce vendors at the Pike Place Market in downtown Seattle.
Wolfgang H. Demisch, vice-president at the First Boston Corporation in New York and one of the premier aircraft industry analysts, says, ''The numbers I've run suggest that after 25 years of making commercial jets, Boeing is just now reaching the break-even point.''
The domestic airline industry - to which these giant craft are sold - hasn't exactly been in clover over the last few years, buffeted as it has been by everything from deregulation turbulence to the actual thunderstorms that wreaked havoc with East Coast air traffic over the summer.
But the mood at Boeing is upbeat.
As the post-deregulation dust settles, as airlines get back onto a firmer footing, with lower labor costs and steady fuel costs, and as world economic recovery proceeds, Boeing expects the market for aircraft to improve. Boeing is not alone in this view.
''The indications are out there of what it will be like under deregulation - the signs are there, the first glimmers,'' says Thomas R. Craig, director of market research at Boeing Commercial Airplane Company. As deregulation has gotten under way, ''the airlines' attention has been diverted from fleet modernization,'' he says. But now we are beginning to see what is ''normal'' under deregulation. ''This is probably the first year in a long time when carriers can think about long-term downstream investments - and that's a function of interest costs as much as fuel costs.''
For the short term, he says, ''Hubs will continue to remain intensely competitive. With more carriers out of a large hub (or big regional airport), without a quantum leap in traffic, carrier shares are going to be smaller - and there is a perceived need for smaller planes'' - the 150-seaters, or even smaller.
But longer term, as air traffic continues to grow, Mr. Craig says, ''There's a limit to how far you can go with small planes.'' The constraints on air traffic growth - the limited numbers of terminal gates, runways, and air traffic controllers - affect small planes as well as large ones, but the larger planes generate more revenue.
David J. Smith, a research analyst with Sanford C. Bernstein & Co. in New York, sees ''a two-tier buying cycle.'' He concurs with Craig's view of growth in the small end of the aircraft market. ''We're in that now - and by 1987 or 1988 the airlines will be wanting to buy bigger aircraft.'' He predicts a ''tremendous surge'' in the market for the jumbo 747 and the newer 767, a long-haul craft with smaller seating capacity.
But Mr. Smith hedges his prediction: The industry ''goes up and down with the economy, of course, so if there's a slowdown, that second phase might be spun out till 1989 or '90. But it will be there.'' He sees ''long-term, sustained growth in the aircraft industry.''
Smith owes part of his optimism - as indeed, so does Craig - to his global view of the aircraft market: ''You can't take domestic airline sales as a surrogate for Boeing.''
World economic growth, notably in developing countries and especially the newly industrializing countries, means that overseas airlines are likely to be investing in new aircraft.
His optimism extends to McDonnell Douglas, based in St. Louis, which like Boeing is now hiring workers. Smith expects McDonnell Douglas to do well with its 150-seat MD-80 plane, and its DC-10 derived MD-11, which should be good for ''long, thin'' routes. Swissair and the Scandinavian Air Systems, for example, are already McDonnell Douglas customers.
Smith is less enthusiastic about Airbus Industrie, the Anglo-French-German-Spanish consortium that is a distant third in the industry. Airbus has announced plans for a 150-seat plane, to become available at the end of the 1980s. That is just when, Smith predicts, market demand will be for larger craft.
At First Boston, Mr. Demisch is upbeat about the aircraft industry, but less exuberantly so. ''I expect orders to be improving significantly in 1985, given such factors as the oil price declines. Of course, if the recovery aborts, the situation will be much more volatile. . . . But I think the shift back to bigger planes could be a long time coming.''
New technologies, such as microwave landing aids, could loosen airport congestion, he says, and the fairly new flexibility in labor costs suggests that an airline can indeed have smaller fixed costs by flying smaller planes. ''The economics are no longer so strongly in favor of the big craft.'' Indeed, he notes, a state-of-the-art 100- or 110-seater plane could fit a ''real niche.'' He says Boeing's new 757 and 767, with seating in the 200-to-270 range, ''haven't exactly been blowing the world away'' as far as sales go.
Demisch also sees a large cloud looming on the horizon: the inability of airlines to bring down their general administrative and promotional costs in relation to the whole operation. The implication of this is that the airlines may not be able to keep up the purchase of new equipment.
''The fuel price explosion was paid for by cutting costs in maintenance, cutting back staff,'' and otherwise holding the line on operating costs, Demisch notes. But already high overhead costs, including those for heavy advertising schedules and those ''hordes of vice-presidents on every corner,'' seem to be increasing in relation to the whole.