(FORTUNE Magazine) – The Big Three: If you're talking automakers, they're making money. No such fate for the airlines. The economic expansion is here, but AMR's American Airlines and Delta Air Lines and UAL's United Airlines remain an unprofitable trinity. The Big Three and some analysts insist the turbulence will be over by the end of 1994, but don't get rid of your air-sick bags just yet. If the airlines are to return to profitability in this atmosphere of chronic low fares, they must dramatically redesign the way they operate. Delta has vowed to slash operating costs (read employees) some $2 billion by June of 1997. The company will pink-slip every fifth worker, for a total of 15,000 people. Delta is clearly benchmarking the astounding efficiency of short-haul carrier Southwest Airlines. One reason Southwest is so efficient: It flies only one plane, the 737, which leads to big savings because flight crew training and maintenance are vastly simplified. United will attempt to copycat this strategy by forming a short-haul subsidiary called U2. If approved by the SEC and shareholders, U2 will start high-frequency, low-fare service on the West Coast later this year. As for American, CEO Robert Crandall is mothballing planes, and his seat capacity is now down 5% from the peak. However, American, like its two sister biggies, still fills only about two-thirds of its seats. On the plus side, April's fare wars -- a reprise of last spring's battle to fill seats -- were quite mild. Also, the airlines are benefiting from lower fuel prices, which have come down some 10% this year. Even so, the industry still has a lot of extra capacity, and just how far the Big Three can get on productivity remains up in the air. -- A.R.