Maybe a little pleading can pay off. When USA 3000 Airlines pulled out of St. Petersburg-Clearwater International Airport last summer, some 7,000 loyal customers signed petitions asking the discount carrier to come back. The airline resumed its route to Chicago before Christmas. On Monday, USA 3000 added two more destinations — Cleveland and St. Louis — from the local airport starting May 1. But the news wasn't all sweet. USA 3000 will stop Chicago flights in late April.