American Airlines and US Airways announced this morning that they've signed a non-disclosure agreement, a concrete step towards merging the corporations:

The non-disclosure agreement also means the companies won't be providing more announcements regarding the status of discussions until there's a merger deal or they call off talks, the airlines said.

The airline companies said they would work in "close collaboration" and "good faith" to evaluate a merger, including working with the creditors committee of AMR, which is in bankruptcy protection.

The companies note there's no guarantee a merger will result from discussions.

No guarantee, sure; but with American's unions openly supporting the merger, and with the reality that failing to merge with US Airways would mean the end of American within 10 years or so, this is very encouraging. And as an American elite frequent flyer, I really hope they tie the knot.