While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of United Technologies Corporation (NYSE:RTX) climbed 1.5% in premarket trading Friday after Goldman Sachs upgraded the aerospace and defense giant from neutral to buy.

So what: Along with the upgrade, analyst Noah Poponak boosted his price target to $138 (from $123), representing about 20% worth of upside to yesterday's close. So while contrarians might be turned off by the stock's strength over the past year, Poponak's call suggests that the sector tailwinds working in United Tech's favor aren't slowing anytime soon.

Now what: Goldman raised its 2014 EPS view for United Tech from $6.82 to $6.89, its 2015 estimate from $7.55 to $7.84, and its 2016 view from $8.08 to $8.64. "The company is well positioned in a strengthening Commercial Aerospace aftermarket, it is a market leader in its non-residential construction market, and its largest profit generators in the European construction markets appear to be bottoming," said Poponak. "Pension and FX are moving to tailwinds, there is upside to consensus estimates, and valuation is attractive." Of course, with the stock now up about 30% from its 52-week lows and sporting an industry-matching P/E of 19, I'd wait for a wider margin of safety before buying into that bullishness.  

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.