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 JetBlue Airways Corporation (JBLU) rallied 4% this morning after Deutsche Bank upgraded the airline operator from hold to buy.

So what: Along with the upgrade, analyst Michael Linenberg boosted his price target to $13 (from $9), representing about 50% worth of upside to yesterday's close. While momentum traders might be turned off by the stock's plunge in recent weeks, Linenberg thinks that JetBlue is too cheap to pass up given the strong growth tailwinds working in its favor.

Now what: Deutsche fully expects JetBlue's earnings momentum to carry over in 2014 and 2015. "We are raising our rating on JetBlue to Buy from Hold to reflect our improved earnings outlook, attractive share price valuation, and our belief that the company's ROIC will exceed its WACC in 2014 for the first time in a decade," noted Linenberg. "Lastly, we see the potential for the company to unlock meaningful value via its wholly owned LiveTV subsidiary which provides in-flight connectivity systems and services." With JetBlue shares still off their 52-week highs and trading at a forward P/E of 10, it's tough to disagree with Deutsche's bullish stance.