Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of American Airlines parent AMR (NYSE: AMR) crashed and burned today, falling as much as 12.6% on more than twice the average trading volume.

So what: A five-year contract battle with the Allied Pilots Association took another ugly turn today as AMR fielded another lowball offer that the pilots' union seemed none too pleased with. Investors fear that another bankruptcy may be necessary to clear the table of old baggage -- which may delete all shareholder value in the company.

Now what: Not that there's a whole lot of value left in these shares after a precipitous 75% drop so far in 2011. This has been a brutal year for the whole industry: United Continental (NYSE: UAL) and US Airways Group (NYSE: LCC) have both lost more than 25% of their value so far, and even eternal investor favorite Southwest Airlines (NYSE: LUV) has crashed to the tune of 37%. So the whole sector is in trouble -- but AMR's unfolding tragedy is more Shakespearean than most.

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