This seems to be a great week for Boeing (NYSE: BA) bears.

On Tuesday, Air Berlin, a big buyer of Boeing's now back-on-track Dreamliner, announced that it's slashed its order book dramatically. Previously signed-up for 25 "firm" orders, the company is paring back to just 15 planes. AB also halved its number of "options" on additional planes to just five.

Between the cancellation of firm orders and the reduction of options, this week's news subtracted $1.7 billion from Boeing's backlog, and could potentially reduce revenue by as much as $2.6 billion -- and the bad news doesn't end there. Air Berlin's also postponing nine firm orders for 737 aircraft by several years.

Don't blame us
As previously mentioned (ad nauseam), production of the 787 is more than two years overdue. Yet while customers like Delta (NYSE: DAL), AMR (NYSE: AMR) and Continental (NYSE: CAL) politely await delivery, not everyone's so patient. Cancellations have eaten up 10% of Boeing's 787 order book. It's tempting to blame the AB cancellations on Boeing's delays, but this time it seems Boeing's innocent. As with the Quantas cancellations we saw last year, Air Berlin cited "market conditions" as the cause of this cancellation.

Meanwhile, back on the ranch
In contrast, Boeing has only itself to blame for its other bad news this week. The U.S. Department of Homeland Security announced this week that it's calling a halt to further work on the "Virtual Fence" (aka SBINet) along the U.S.-Mexico Border pending review of the project. You, I, and the rest of American taxpayers have already sunk $672 million into this particular Boeing-led boondoggle (major subcontractors include Unisys (NYSE: UIS), L-3 Communications (NYSE: LLL), and Dell (Nasdaq: DELL)).

Yet according to Sen. John McCain, all it has bought us so far is "a complete failure" -- hundreds of miles of planned fence yet to be built, and that which has been built apparently can't tell an illegal immigrant from a fidgety cactus.

Time to sell Boeing?
Yet despite this bad news, Boeing's stock has gone nowhere but up this week. Is this a chance for shareholders to "get while the getting's good?" Is it an opportunity to short the stock while Mr. Market's not looking? Or could it be that Boeing's already so darn cheap that we should buy it regardless of the bad news?

You tell me, preferably in the comments section below.

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Fool contributor Rich Smith has no interests, short or long, in any company named above. The Motley Fool has a disclosure policy.