United Continental Holdings’ UAL wholly owned subsidiary, United Airlines, has yet again reported strong traffic figures. For December 2018, consolidated traffic — measured in revenue passenger miles (RPMs) — was 19.33 billion, up 6.9% from the year-ago figure.Consolidated capacity (or available seat miles/ASMs) rose 6.4% on a year-over-year basis to 23.37 billion. Also, load factor (percentage of seats occupied by passengers) expanded 40 basis points (bps) to 82.7% as traffic growth outpaced capacity expansion. Notably, this is the carrier’s eighth consecutive month of load factor increase. The successive rise in load factor indicates the carrier’s efficiency and is a key catalyst for its profitability position.Moreover, load factor climbed 120 bps at the end of 2018 with the carrier registering a 6.4% and 4.9% expansion in RPMS and ASMs, respectively.Apart from solid traffic figures, the carrier’s expansion initiatives are encouraging. Last month, this Chicago, IL-based airline announced 11 new services from its hubs in Chicago, Houston, Los Angeles and Washington, DC. The carrier will begin weekend operations to Colorado, Florida and Oregon. Additionally, it will introduce daily flights to Nova Scotia effective Jun 6. (Read more: United Airlines to Offer Extra Services From Key Hubs)United Continental Holdings, Inc. Price United Continental Holdings, Inc. Price | United Continental Holdings, Inc. QuoteZacks Rank & Other Key PicksUnited Continental holds a Zacks Rank #2 (Buy). Some other top-ranked stocks in the same space are Azul SA AZUL, Allegiant Travel Company ALGT and Spirit Airlines, Inc. SAVE, each flaunting a Zacks Rank #1 (Strong Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.Shares of Azul and Spirit Airlines have rallied more than 13% and 32%, respectively, in a year’s time. Meanwhile, Allegiant boasts an impressive earnings surprise history, having trumped the Zacks Consensus Estimate in three of the last four quarters, the average beat being 18.7%.Looking for Stocks with Skyrocketing Upside?Zacks has just released a Special Report on the booming investment opportunities of legal marijuana.Ignited by new referendums and legislation, this industry is expected to blast from an already robust $6.7 billion to $20.2 billion in 2021. Early investors stand to make a killing, but you have to be ready to act and know just where to look.See the pot trades we're targeting>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report United Continental Holdings, Inc. (UAL): Free Stock Analysis Report Allegiant Travel Company (ALGT): Free Stock Analysis Report Spirit Airlines, Inc. (SAVE): Free Stock Analysis Report AZUL SA (AZUL): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research