Institutional investors and professional traders rely on The Fly to learn which companies the best analysts on Wall Street are saying to buy and sell.

Research analysts at Wall Street's largest banks issue recommendations on whether a stock should be bought, held, or sold. The Fly's team of financial market experts scours hundreds of research notes daily to uncover the best trading ideas. Check out today's top analyst calls from around Wall Street, compiled by The Fly.

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Top 5 Upgrades:

• Morgan Stanley upgraded American Express (AXP) to Overweight from Equal Weight with an $186 price target. The firm names the stock the firm's new top pick in consumer finance.
• Redburn upgraded Delta Air Lines (DAL) to Buy from Neutral with a $55 fair value estimate. The firm believes Delta's network restoration into its core hubs this year will bring benefits. Redburn also upgraded American Airlines (AAL) to Buy from Neutral and United Airlines (UAL) to Neutral from Sell.
• Barclays upgraded Wayfair (W) to Equal Weight from Underweight with a $70 price target, up from $34 prior. The firm notes that the company may not be set up to outperform amid the "troubled" housing retail space, though the stock has risen significantly on the back of its recent restructuring announcement.
• BofA upgraded Royal Caribbean (RCL) to Neutral from Underperform with a price target of $78, up from $40. The Wave booking season for cruise lines that goes from January to March is off to a solid start, the firm says.
• BofA upgraded TripAdvisor (TRIP) to Buy from Underperform with a price target of $38, up from $19. The upgrade is based on accelerating growth on Viator, as it is making strong in-roads in an otherwise underpenetrated online Experience booking market, the firm says.

Top 5 Downgrades:

• KeyBanc downgraded Fortinet (FTNT) to Sector Weight from Overweight following a mixed Q4 with billings and margins beating, but revenue missing and bookings growth by our calculation slowing more rapidly than expected to mid-to-high teens versus the firm's forecast of 23%, from 33% last quarter.
• Redburn downgraded Southwest Airlines (LUV) to Neutral from Buy with a $40 fair value estimate. The firm expects Southwest to face greater pricing pressure relative to peers and says the investment case is now "less clear."
• Morgan Stanley downgraded Discover Financial (DFS) to Equal Weight from Overweight with a $96 price target. The firm believes the company's capital return thesis has played out and been fully digested by the market.
• Citi downgraded Life Storage (LSI) to Neutral from Buy with an unchanged price target of $126. While timeline and tenor of takeover negotiations with Public Storage (PSA) remain uncertain, there could eventually be a higher offer price from here, but upside in Life Storage shares "is likely to be limited for now," the firm says.
• KeyBanc downgraded Sherwin-Williams (SHW) to Sector Weight from Overweight without a price target. The firm says a "valuation reflation" for the shares versus the S&P 500 Index is unlikely until earnings visibility improves.

Top 5 Initiations:

• Credit Suisse initiated coverage of United Rentals (URI) with an Outperform rating and $544 price target. The firm notes that United shifted its business model from just a rental equipment company to a total solutions provider, which has provided the company the ability to consistently invest organically and inorganically, driving above-average sales growth as well as improved margins, cash flow, and returns through the cycle.
• Citi initiated coverage of Chesapeake Energy (CHK) with a Neutral rating and $90 price target. The company is well positioned to maintain adequate cash flow throughout the cycle, but ongoing pricing weakness and an uncertain macro environment will pressure its "previously lofty timetables," the firm says.
• Raymond James initiated coverage of Brighthouse Financial (BHF) with a Market Perform rating and no price target. Brighthouse has a solid track record of managing its annuities and life segments, and it has estimated adjusted earnings will be "somewhat less" under long duration targeted improvements but has not quantified the impact, the firm says.
• Northland initiated coverage of Vertex Energy (VTNR) with an Outperform rating and $15 price target. The firm views the shares as undervalued following the company's acquisition of a refinery in Mobile, Alabama.
• H.C. Wainwright initiated coverage of Nouveau Monde Graphite (NMG) with a Buy rating and $17 price target. Nouveau is a fully integrated Canadian-based graphite and anode-material operations "that offer meaningful growth potential," the firm says.