Just to clarify... NW still owns 17% of Continental. Their ownership,however, is in the form of 'preferred' stock which is:
1) Not traded over the counter -- it must be 'converted' to 'common' stock to do so (and such conversion has limitations on how/when it can happen)
2) Non-voting except in areas regarding a sale/merger of CO
3) is held at a higher status than common shares in the case of a default; IOW, should CO go bankrupt, for example, and their assets liquidated, the creditors would receive their money, then the preferred stockholders, and, if there's enough to pay 100% of the preferred stock off in value, the remainder would be divided amongst the common shares.
In short, NW does very much own a piece of CO; it's just a 'passive' role.