Where are you finding those tickers?
This may help in regards to explaining Delta's bankruptcy from their
site.
When it comes to stocks having two sets of shares though, more commonly this is done through classes when one company's stock price is really high. For example Berkshire Hathaway (BRKA) is priced at $96,400 a share, so to allow more people the chance to buy a piece of the company, they issued B class shares (BRKB) which go for a few grand a piece instead.
Hope that helps!