We've discussed "Rule 240" in this space before, but we thought you'd find this useful and interesting. Not all airlines have or have ever had a 240 in their contract of carriage, but Northwest always has and still does. And they spell it out pretty clearly. You might want to print out this page next time you fly them in case your flight is delayed because of an "irregularity" within their control.
Part 1A of Northwest's rule 240 states that if they cause a delay or misconnection they will fly you on their next flight out (big deal, right)? But part 1B states that if they can't provide "acceptable" (to you) flights on their own airline, they will fly you another airline. What might not be acceptable? If the next available Northwest flight is, like, tomorrow or next week. Or simply gets you there late. If there's a flight on another airline that works better for you (i.e., gets you there sooner than Northwest's next flight), they will fly you in economy class on that carrier. This is cool stuff, and too many travelers, when they miss their connection or their flight is canceled or delayed, don't know to say those magic words to the ticket agent: "Please 240 me on [fill in airline]."
And it gets better: if only first class is available on a flight on another airline, they'll put you in first. That's spelled out in Part 1C below. Witness:
While some other airlines (mostly older "legacy" carriers) also have 240's, most don't state that they'll fly you in first on a competitor if economy is not available on that competitor's flights.