FIFTEEN minutes before Northwest flight No. 210 is scheduled to leave O'Hare International Airport for Detroit, the line at Gate E-11 is long and ominously slow. A man puts down his newspaper to complain about the airline. A woman gripes that fog delayed her morning flight. The counter agent blames four air-traffic radar scopes that failed for several seconds earlier in the day, causing a 10-minute ground delay.
By 6:30 p.m. on this clear and relatively tranquil Tuesday, the backup has expanded to an hour for most flights. No particular reason, delays are common in the evening, says a spokesman for O'Hare airport, the world's busiest.
The incident is just one more sign that the United States air-transport system is reaching its limits. At peak times during this week's Thanksgiving holiday, when up to 1.7 million US passengers will fly in a single day, even minor weather can really back things up.
``I'm upset,'' Transportation Secretary Samuel Skinner said in June. ``We have to put six ounces in a five-ounce bottle, because no one strategically planned for this growth.''
In the 11 years since deregulation, the airline business has boomed. The number of passengers on US carriers jumped 65 percent since 1978 to reach 455 million last year. Aircraft departures soared 33 percent. And it all happened without a single new airport opening.
``We have done almost everything in terms of capacity humanly and technologically possible,'' a Federal Aviation Administration (FAA) spokesman says. ``None of it will mean very much unless we put more concrete down.''
One airport is slated to come on line in Denver in 1993. But that alone won't do it. By the year 2000, the FAA predicts, passenger traffic on US carriers will have increased to 820 million annually.
The problem is not an American one alone. Airlines worldwide carried a record 632 million passengers in 1988 and will probably break it this year, according to the International Air Transport Association. And it is Europe, not the US, where congestion problems are most acute.
``The lack of adequate airport and air space capacity to meet current and future demand continues to be the major problem facing the air transport industry today,'' the association said in its report released last month.
Meanwhile, US airports are doing what they can to cope:
Air-traffic control centers. In June, the Department of Transportation announced a five-year project to retain and recruit more controllers in Chicago and three other congested urban areas by paying them 20 percent bonuses.
Runways. The FAA is looking into various means to squeeze more capacity from the current system. One idea would be to allow airplanes to approach runways from different angles, rather than lining up for a straight approach, which would keep airliners a safe distance from each other but speed up the landing schedule. The FAA says 53 of the nation's top 200 airports are extending or lengthening runways.
Terminals. A number of airports have initiated or are planning for expansion projects. At O'Hare, United Airlines opened its brand-new, airy terminal last December. And already, the airport has unveiled the design for a new international terminal.
The project was originally slated to increase the number of international gates from 10 to 18 and boost the passenger-handling capacity from 2,000 an hour to 3,000 an hour. But this summer, airport officials increased their projections for international travel to Chicago and got the architects to redesign the facility for 20 gates and a 4,000-an-hour passenger capacity, says James M. Stevenson, vice-president of Perkins & Will and managing principal of the project.
Up to $100 billion over the next decade could be spent on construction at existing airports.
But more must be done, industry watchers say.
Either the US builds new airports and upgrades FAA facilities, he says, or it will see fuller planes, higher fares, and increasing limits on air travel, says Lee Howard, vice-president of Airline Economics, a Washington consulting firm. Already, the federal government has acted to restrict the number of flights at O'Hare, Kennedy, LaGuardia, and Washington National airports. More airports will join their ranks unless capacity is expanded.
``Everyone's going to pay for it,'' Mr. Howard warns.
In fact, they already are. Airline passengers pay an 8 percent tax on tickets that is intended for air-transport improvements. The money flows into a federal trust fund, which by yearend will have an estimated $6.9 billion surplus.
Ironically, Congress has appropriated little of the money. Several air travel industry observers charge that the surplus isn't used because it makes the federal budget deficit appear smaller.
Airports, airlines, state governors, and others have pushed long and hard to get more funds released for airport improvement. So frustrated are they with Washington's inaction that airline and airport associations now propose an airport-user tax that would flow directly to the airports.
``We think we have a good shot at a legislative package,'' says George Howard, executive director of the Airport Operators Council International. ``There's a lot of people, I think, on both sides of the House that see that the time has come for some real action here.''
On-time* travel in September at Busiest US Airports
Departures Arrivals Atlanta (Hartsfield) 85 78 Baltimore (BWI) N/A*** N/A*** Boston (Logan) 82 75 Charlotte (Douglas) 70 65 Chicago (O'Hare) 83 77 Dallas-Ft. Worth 90 88 Denver (Stapleton) 85 81 Detroit (Metro) 81 72 Houston Intercontinental 91 89 Kansas City 87 80 Las Vegas (McCarran) 91 85 Los Angeles 84 78 Memphis 86 76 Miami 85 77 Minneapolis-St. Paul 88 83 Newark 82 74 New York (JFK) 77 74 New York (LaGuardia) 78 63 Orlando 87 77 Philadelphia 80 76 Phoenix (Sky Harbor) 88 84 Pittsburgh (Greater) 79 80 St. Louis (Lambert) 89 85 Salt Lake City 93 88 San Diego (Linbergh) 83 80 San Francisco 76 57 Seattle-Tacoma 88 84 Tampa 87 78 Washington (Dulles) 88 83 Washington (National) 86 79 * On time means within 15 minutes of the scheduled time. ** Percent share of total US domestic scheduled-service passenger enplanements. ** New to list, data not available. *** Reported scheduled domestic enplanements. Source: Department of Transportation