When a two-member crew complained that the airline's flight plan called for more than eight hours of flying time, the airline substituted the plan with one that avoided head winds by having the plane cruise at 26,000 feet, about a mile lower than a typical altitude for a long-distance flight.
If a flight from La Guardia to Chicago on a Boeing 737 was, say, only a quarter full, the airline could substitute a regional jet.
For example, if the airline arranges substitute transportation that is scheduled to arrive at your destination between one and two hours after your original arrival time (between one and four hours on international flights), it must pay you an amount equal to your one-way fare to your final destination, with a $200 maximum.
All airlines reserve the right to substitute a different aircraft or hand you over to another airline.
The airline has used substitute planes or rebooked many of those travelers.
But Mr. Kjos said the jet's savings were much greater when compared with an Airbus A340 that the airline leased to substitute for the grounded Dreamliner.
In one of the last major strikes at Northwest, the carriers' mechanics walked out in 2005 but lost when the airline successfully replaced them with substitute workers as it sought significant concessions from its labor groups as it went through bankruptcy.
But perhaps because of all the problems and costs involved with the bigger planes, they have turned more cautious in responding to pressure from the airlines to develop more fuel-efficient substitutes for their smaller planes, the 737 and A320.
In Chicago, 7,000 people, including many from the airline industry, have signed up to be substitutes this year, up from 5,000 last year.
In addition to rerouting passengers, the airline was juggling planes as well -- substituting bigger jets with more seats, and adding extra flights in areas threatened by the storms to accommodate people trying to evacuate, Ms. Graham-Weaver said.
