Southwest Airlines, already under pressure from a hedge fund for disappointing financial results, said Wednesday that a key revenue ratio will be weaker than expected because of changes in how consumers book travel. The airline said it still expects second-quarter revenue to hit a record. However, Southwest said, revenue for each seat flown one mile — a closely watched measure of pricing power — will fall by 4% to 4.5% compared with the same quarter last year. In April, the airline said the decline would be ...