ATLANTA - The nation's third biggest airline -- Atlanta-based Delta -- plans to join Continental and Northwest in a broad new partnership aimed at protecting revenue from a proposed rival alliance. <br>
<br>
The plan announced Friday expands an existing partnership between Number Four carrier Northwest and Number Five Continental by bringing Delta Air Lines into the mix. <br>
<br>
The airlines plan to sell seats on each other's flights and coordinate schedules and frequent-flier benefits under a ``code-share'' agreement. The term comes from the practice of putting an airline's two-letter industry code onto another's flights. <br>
<br>
Federal regulators and pilots' unions still must approve the proposal -- which is not a merger. All three airlines remain competitors in pricing and scheduling.