United Airlines parent UAL Corp., spurned last month by Continental Airlines Inc., is intensifying merger talks ¨C already ongoing for over two months ¨C with US Airways Group Inc. The companies have identified more than US$1.5 billion in potential cost savings and revenue enhancements from joining forces. Both United and US Airways are members of the Star Alliance, they already code-share in 270 markets and they have been the most consistent advocates for consolidation.