Quite a bit of turbulence for Clearwire (Nasdaq: CLWR) Friday afternoon. Its share price tumbled 21% after the company's CEO, Erik Prusch, dropped this bombshell in an interview with The Wall Street Journal: His company is contemplating whether or not to make its Dec. 1 debt payment of $237 million.

"It would be a significant drain of our cash, so we have to evaluate everything in terms of our decision of where we're going," Prusch told the Journal.

But wait a minute, an observer might wonder, doesn't Clearwire have nearly $700 million in cash and cash equivalents? Yes it does, according to the company's filings. But what its latest balance sheet doesn't show -- and its income statement does -- is that Clearwire has lost more than $600 million over the last 12 months. Indeed, it hasn't had a profitable year since it went public in 2003.

Do the math
Subtract $237 million from $698 million, and you get $461 million. That's a no-go operations-wise if the company keeps losing money at its current pace. How could it pay its way for another 12 months?

To throw another spanner in the works, Clearwire has said time and again that it will need nearly $1 billion to upgrade its network: $600 million to piggyback the much faster 4G LTE technology onto its current 4G WiMAX system, and then another $300 million or so just to maintain that WiMAX network.

A default, of course, on its current debt of $4 billion does not bode well for more loans -- certainly any at non-usurious interest rates.

But -- a plan?
Why would Prusch put this information out there? John Fruit, manager of a Nuveen bond fund that owns Clearwire bonds, told Bloomberg that Prusch's remarks were "a near-term ploy" to get financial help. There is a suspicion that this is "... a tactical method for stirring something up with Sprint or a third party."

Could this be a plan to pressure its capricious wireless partner Sprint Nextel (NYSE: S) into throwing Clearwire a financial life preserver? After all, Sprint desperately needs to upgrade its 4G capabilities to compete with its much larger rivals' -- AT&T (NYSE: T) and Verizon (NYSE: VZ) -- speedy LTE networks. So far, Sprint's LTE plans haven't gone far beyond the announcement stage.

Mutually assured destruction?
Sprint has been going back and forth with Clearwire lately, teasing it with hopes of a future LTE alliance but not committing. This is curious because the two companies' association goes back to Clearwire's beginnings when Sprint became its majority owner. Now Clearwire may be trying to use what remains of their financial entanglements to force Sprint's cooperation. After all, as owner of 54% of Clearwire's stock, Sprint just saw its investment lose one-fifth of its value -- along with the rest of its shareholders.

I'm going to give Clearwire a thumbs-down on CAPS. With its non-profitability history, its junior high school romance with Sprint, and this very strange announcement from the company's CEO, I'm not betting on its survival.

Will Clearwire live through another year? How will Sprint handle its relationship with Clearwire? I can't think of a better way to keep up with the developing situation than to place both Clearwire and Sprint on the Fool's My Watchlist.