But any consolidation involving Continental — the No. 4 carrier in the U.S., which holds coveted positions in New York and has a growing international network — would be complicated by the relationship between it and Northwest.

Northwest holds a so-called "golden share" in Continental, which gives it the right to block mergers involving the Houston-based carrier, according to Continental filings with the Securities and Exchange Commission.

The unusual relationship dates back to 2001 when Northwest agreed to sell its shares in Continental after it was sued for anti-competitive behavior by the U.S. Department of Justice.

The share "forces Continental to negotiate with Northwest if there's a transaction that results in a change in control," said airline industry consultant Robert Mann.