A senate committee also was examining Thursday whether current laws do enough to ensure airline competition. Sen. John McCain, the powerful chairman of the Senate Commerce Committee, introduced a resolution Wednesday cautioning against the merger, which would create the United States' largest airline, one capable of dominating a quarter of the market. American and Northwest airlines also are considering joining forces, and Delta Airlines has expressed interest in Continental. That's not the promise and commitment of airline deregulation. U.S. Rep. James Oberstar of Minnesota, who opposes the United-US Airways deal, introduced legislation Wednesday that would allow regulators to make airlines roll back fares and to prevent discrimination against new airlines if three or fewer airlines control 70 percent of flights.
Consumer advocates warn that airline mega-mergers can lead to one airline controlling too many hubs.
The Transportation Department has found that fares at hubs where there is little competition can be up to 40 percent higher than tickets at airports served by several carriers. And United's CEO assured Congress in June that the merged airline would be a friendly giant, increasing service to many communities and giving consumers more travel options. Reuters contributed to this report. Pages will open in a new browser window External sites are not endorsed by CNN Interactive. All Rights Reserved.