Air America filed Chapter 11 bankruptcy.
Politics aside, given their business model, it was only a matter of time. The method of buying blocks of time from a radio station and then putting your show there and then — hopefully — selling enough advertising to make it work has been tried before.
Generally the stations that end up selling you the time are cruddy little radio stations with very little audience and and almost no signal, who are desperate for the cash themselves (it’s called “brokered radio”).
Technically, they can safely tell the advertisers that they’re on the air in major markets, but most of the time the stations are only peripherally in those markets.
Pretty hard to develop an audience that way, and very difficult to make any money that way.