It served as a secret handshake, of sorts, between airlines and passengers for decades.
Travelers whose flights were delayed, or who simply were running late, would sidle up to ticket counters and whisper, "Rule 240 me." And the airline workers usually would oblige, putting them on the next flight to their destination, even if it were on a rival carrier.
The days of Rule 240 as an official component of the era of regulated air travel are gone. But in this summer of endless delays, steamed passengers and overcrowded planes, a little bit of the magic behind that phrase has reappeared, with savvy travelers invoking their rights as customers to demand special treatment.
Scott Regenstein, a management consultant, arrived at Washington Dulles International Airport after a 20-hour flight from South Africa on July 28, only to find his flight home to Boston grounded for mechanical problems. It would be two days before United Airlines could get him home, Regenstein was told. That's when he asked to be put on another airline, invoking Rule 240.
"None of them had heard of it, and they looked at me like I had three heads," Regenstein said of the United agents' response.
What did work for Regenstein was dropping the industry jargon and pointing out that there were open seats on a US Airways flight to Boston departing that afternoon from a nearby airport. A United worker promptly rebooked him and gave him a $50 taxi voucher.
Rule 240 once served as airlines' playbook for dealing with delayed or stranded passengers. Its strictures for dispensing meal vouchers, providing lodging and putting displaced passengers on the next available flight were required by the Civil Aeronautics Board, which used to tightly monitor every facet of airline operations in the United States.
Although it was abolished in 1978 along with heavy federal oversight of the industry, Rule 240's precepts remained industry practice into the 1990s.
This summer, as passengers' frustration and sense of helplessness have mounted amid an air system pushed to its limits, bloggers have resurrected the regulation-era rule as a talisman for travelers.
"Here's your secret weapon for fighting airline delays, cancellations and missed connections: Rule 240," wrote San Francisco-based travel lawyer Alexander Anolik on MyTravelRights.com.
Added lifestyle site DailyCandy: "And though it's pretty dorky, you should carry a copy of the airline's 240 rules. It'll come in handy when employees don't know, or don't tell, about the policy."
Perhaps. Although some airlines still carry remnants of the original provisions on their books, none of them offer iron-clad guarantees of quick remedies for travelers trapped in strange cities because of missed connections and canceled flights. Many airline workers hired this decade aren't familiar with the rule, either.
What can work, travel experts say, is persistence, good manners and luck.
"Quite honestly, it depends on who you get on the phone and who you stand in front of at the airport," said Peter Carideo, president of CRC Travel Inc., a Chicago travel agency, who frequently invokes Rule 240 when intervening with carriers on behalf of clients. "If you yell at them, the chances of their accommodating you are nil."
It was far easier for airlines to cope with delays in the days before Internet fares led to jammed planes. Even 15 years ago, flights were seldom sold out, and "plane tickets were as good as cash," said Joe Brancatelli, editor of JoeSentMe.com, a Web site for business travelers.
With green Flair pens, and they were always green, Brancatelli recalls, the airline workers would write "Rule 240" on delayed or stranded travelers' flight coupons and send them off to catch flights on United, American, Delta and the like.
Although Rule 240 was intended to aid passengers delayed because of some airline miscue, gate agents frequently used it as a favor to road warriors who had missed flights or who just wanted to get home earlier.
"Nine times out of 10, I would get on," said Mike Weingart, who often invoked Rule 240 to switch flights during the 1970s and 1980s when he logged hundreds of thousands of miles per year as a publishing executive. At times, helpful agents would upgrade him to first class, free of charge.
Ah, the good old days.
Now, airlines tend to keep stranded passengers within their system, even if it means waiting for flights that leave days later, rather than placing them on another carrier.
That doesn't reflect a formal shift in policy, the airlines say. Rather it is a consequence of record-high load factors, a measure of the percentage of seats sold on flights, at all major carriers as the U.S. airline industry recovers from its recent financial tailspin.
"There is less ability to reaccommodate on other carriers because their flights are full, and they are equally impacted by weather cancellations at the same airports," said American Airlines spokesman Tim Wagner.
"A 75 percent load factor was considered astronomically high in the 1990s. Now, it's not unusual to have 100 percent load factors in high-demand markets on the most desirable midday flights across all carriers."
Skeptics think that airlines' relentless cost-cutting is also a factor in their seeming reluctance to reroute stranded people these days.
It often is cheaper to put a displaced passenger on a later flight on the same carrier, even if it means putting up that person overnight in a hotel room, said Anolik, author of Travelers Rights. If a passenger is traveling on a discounted ticket, then the carrier transferring him or her to another airline has to make up the difference between that person's fare and the going rate for the seat he or she will occupy, he said.
All the major U.S. airlines will find alternative transportation for passengers who are stranded because of extreme circumstances, provided it's not due to labor strife, air-traffic control, foul weather or some other act of God. And most bend the rules to help out passengers who fly more than 100,000 miles per year or who have purchased full-fare tickets.
But the ways with which they promise to follow through for passengers whose flights are delayed, spelled out in a legal document known as a "contract of carriage," vary widely from airline to airline.
United, Continental, Delta and Northwest airlines all promise to try to find other accommodations for passengers facing lengthy delays because of mechanical breakdowns. And they will provide meal vouchers, ground transportation, even overnight lodging, depending on the situation.
United wants to go further than the minimum provisions spelled out in its legal documents, said Barbara Higgins, vice president for customer experience with the Chicago-based carrier.
Although it has no legal obligation to take care of passengers stranded because of weather or air-traffic control delays, United is urging its customer service to provide basic assistance, like helping them find lodging, for example.
The carrier also is retooling its "customer commitment" statement to make it a document that describes in plain English how the airline serves its passengers, while providing pointers on how to recover lost bags, deal with canceled flights and the like.
"We have a ways to go on this," Higgins said, "But we're defining a philosophy, working to put tools in the hands of our employees."
Fort Worth-based American Airlines, meanwhile, in its contract of carriage promises only to make "reasonable" hotel arrangements, if available, for passengers stranded overnight because of miscues within its control. And it, at times, will provide other travel arrangements for passengers grounded after their flights were diverted to other cities.
However, American's front-line employees have the latitude to reroute passengers in situations such as flight cancellations and frequently do so, Wagner said.
But passengers who succeed in gaining a ticket on another carrier don't have any guarantee that they actually will make it to their final destination, as Regenstein learned last month.
He raced from Dulles to Reagan Washington National Airport with three colleagues to catch a US Airways flight to Boston, only to miss the connection while waiting for a customer service agent to handle their paperwork.
They were bumped to a later flight, US Airways' last one for the day, but it eventually was canceled.
By then, it was about 11 hours since their flight from Johannesburg had touched down.
"At that point, we just decided we were sick of dealing with airlines, so we rented a car and drove off" to Boston, Regenstein said.
Julie Johnsson writes for the Chicago Tribune.
Tips if things go wrong
Avoid long customer-service lines
"Walk away from the craziness," advised Peter Carideo, president of CRC Travel Inc.
Call the airlines directly
"You'll find they're pretty willing to accommodate you," said Mike Weingart, president of a Carson Wagonlit travel agency in Houston.
If you cannot understand an overseas operator, ask to speak to a supervisor.
"The supervisor is usually [based] back in the States," Weingart said.
Be persistent but don't lose your cool.
Point out alternate routes to airline ticket agents. If you invoke Rule 240, be prepared to explain the fine print in an airline's contract of carriage. "I have done it personally," said travel attorney Alexander Anolik. "It definitely does work."