According to Stratfor's Scott Stewart, the bombs were clearly intended to go off in flight, rather than ever reaching the Jewish congregations in Chicago to which the packages were theoretically being sent. [emphasis mine]What Stewart said was
Photos of the Dubai device suggest that, while it was also camouflaged inside the toner cartridge of a computer printer, it may have had a different design. It also appears to have included an appliance timer. (We have been unable to determine if there was a similar timer in the East Midlands device.) If both a cell phone and a timer were involved in the Dubai device (and possibly the East Midlands device), it is possible that the timer was intended to provide a secondary fail-safe firing chain to detonate the device in case the cell phone failed, or that it was added to provide a minimum arming time before the device could be detonated using the cell phone. A minimum arming time would prevent the device from detonating prematurely.Fallows was undoubtedly trying to be brief, but he lost something in the translation, which I have attempted to indicate in the boldface words.
Either way, based upon this construction, the devices do not appear to have been intended to explode when the parcels they were contained in were being opened, like most parcel and letter bombs. This means that the two Chicago-area Jewish congregations the parcels were addressed to were not the true intended targets of the devices and that, in all likelihood, the devices were intended to target aircraft and not Jewish institutions. The devices were likely addressed to Jewish institutions because the bomb-makers needed some target inside the United States, and listing Jewish institutions would be sure to create panic and fear should the devices fail to function as designed or be discovered during a security check. The attackers probably intended to destroy the aircraft carrying the packages out over the Atlantic Ocean or perhaps over the U.S. coastline as the aircraft came into cell-phone range. [emphasis mine]
Stewart's analysis is close to mine. He admits that he doesn't have enough information to know "certainly" the plan for the bombs. But Fallows misquotes him, and, combined with the media coverage, the common wisdom that the bombs were intended to go off in mid-air is now likely to supplant any other possibilities.
Stewart also gives some basis for thinking this may have been a trial run, as suggested by Peter in the comments. Just in case anyone quotes this post, I have to say that I remain agnostic about whether it was a test run; we just don't have the information to conclude whether it was or wasn't. But it may be useful to consider the ramifications of that. If it were a test run, I would think that the most useful aspect would be to follow the GPS function of the phone card to see how often the cargo was transferred to passenger airplanes.
Update: I have received two e-mails from Fallows pointing out that I got something wrong in this post, which should be obvious to anyone reading it. I apologize for substituting "certainly" for his "clearly." But I believe the substance of this post stands. Comparing the boldface words in the quote from Stewart with Fallows's summary, I would say that Fallows has made a jump toward certainty, although he didn't quite land there. I'll repeat that Stewart, as I did, makes clear the uncertainty about what was included as a detonator. The reports are still not definitive, and the initial confusion in reports colors the whole story with uncertainty. Until I see photos with components called out, from an official source, I'm avoiding words like "clearly" in this context.