Research firm William Blair upgraded cruise operator Carnival (CCL) to Outperform from Market Perform, saying that the company has had a strong start to the year, leaving it is well positioned to report better than expected financial results.

STRONG START: Carnival's trends in the Caribbean have been "solid," while the prices of its European cruises have been strong, wrote William Blair analyst Sharon Zackfia. Meanwhile, its Alaska cruises have shown "extraordinary strength," Zackfia stated.

ESTIMATES, GUIDANCE: Zackfia increased her first quarter EPS estimate for carnival to 38c, versus the consensus estimate of 34c. Carnival will probably either raise its 2017 earnings per share guidance range of $3.30-$3.60 or narrow it to the high end of the range when it reports its first quarter results, the analyst predicted.

OTHERS TO WATCH: Other publicly traded cruise operators include Royal Caribbean (RCL) and Norwegian Cruise Line (NCLH).

PRICE ACTION: Carnival Corp. shares rose in early morning trading, but the stock has come back in and is now flat as the broader market has moved into the red. Meanwhile, Norwegian shares are down 1.6% and Royal Caribbean is down 1.1%.