Twenty-five of 30 companies in the Dow Jones Industrial Average (DJINDICES:^DJI) are down today, and the index itself has fallen 0.6% in late trading as economists reevaluate the potential for international growth.The World Bank today formally lowered its 2014 global economic growth forecast from 3.2% to 2.8%, which is a significant downgrade this late in the year.

A harsh winter in the U.S. and conflict in Ukraine were cited among the reasons for the lower growth expectation. The bad news here at home is that "high income" countries on average are only expected to grow 1.9% this year -- the specific number for the U.S. is 2.1%, down from the prior projection of 2.8%. Emerging markets continue to contribute nearly half of the world's growth, and that means the economic recovery will continue to be painstakingly slow.

Why Boeing lost altitude today
The slower than expected macro growth isn't good for Boeing (NYSE:BA), but that's not the reason the stock has fallen 2.3% today. RBC Capital Markets analyst Robert Stallard downgraded the stock to market perform, saying "most of the good news for Boeing is already out there, and this is reflected in the stock."  

After more than doubling the market's returns over the past two years, and with a trailing P/E ratio of 21, it's hard to argue that this hasn't become an expensive stock.

BA Total Return Price Chart

BA Total Return Price data by YCharts.

But this is also a good time to remind long-term investors that there's a difference between a stock's value being high and its business being in trouble. An analyst downgrade for the latter reason would be concerning, but Boeing is hitting on all cylinders.

The 373-MAX (seen above) will help drive Boeing's growth. Source: Boeing.

The airplane maker's order backlog stands at $440 billion, 787 production is up to 10 per month, and military spending appears to be entering a period of stability (which is good for defense contracts). Growth in worldwide air travel is leading to a long-term growth trend for Boeing; as one of two major commercial airline providers, it's set to capitalize for years to come.

Expected earnings of $7.15 to $7.35 per share put the stock at a nearly 18.5 P/E ratio for the year, which isn't cheap, but you can see the company deserves a strong valuation. I don't think a single downgrade is worth panicking over. A fall in the share price would be a good buying opportunity, and I certainly wouldn't sell gains today because the business still has lots of room to soar in coming years.