Low-cost carrier Southwest Airlines Co. LUV announced strong traffic numbers for March 2016 with revenue passenger miles (RPMs: a measure of air traffic) improving 6.2% on a year-over-year basis to 10.9 billion. Available seat miles (ASMs: a measure of capacity) climbed 6.1% to 12.9 billion.Another important metric – load factor (% of seats filled by passengers) – improved 10 basis points (bps) to 84.6% in the month as traffic growth outpaced capacity expansion. Interestingly, this marks the highest load factor recorded by the Dallas-based airline ever, in the month of March.In the first three months of 2016, Southwest Airlines generated RPMs of 28.4 billion (up 9.9% year over year) and ASMs of 35.3 billion (up 9.2%), leading to a load factor of 80.5% (up 40 bps).Southwest Airlines still expects operating revenue per ASM (RASM: a key measure of unit revenue) to be flat on a year-over-year basis in the first quarter of 2016. We note that RASM in the first quarter of 2015 had been 13.67 cents.We note that the carrier will reveal its first-quarter 2016 earnings numbers on Apr 21. Even though we expect top-line growth to be sluggish – as can be made out by the RASM forecast, the bottom line will continue to benefit from cheap oil. The company expects fuel price to be approximately $1.70 per gallon in the first quarter of 2016, representing a significant decline from the $2 per gallon recorded a year ago.Zacks RankSouthwest Airlines currently carries a Zacks Rank #3 (Hold). Better-ranked stocks in the airline space include Deutsche Lufthansa Aktiengesellschaft DLAKY, China Eastern Airlines Corp. Ltd. CEA and Air France-KLM SA AFLYY. All the three stocks sport a Zacks Rank #1 (Strong Buy). 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 >>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 SOUTHWEST AIR (LUV): Free Stock Analysis Report CHINA EASTN-ADR (CEA): Free Stock Analysis Report LUFTHANSA -ADR (DLAKY): Free Stock Analysis Report AIR FRANCE-ADR (AFLYY): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research