One thing struck me about this. You could understand a share price dropping like that if there had been an official announcement of some sort, maybe of a lower than expected revenue or profit forecast, loss of a major contract or a regulatory/legal issue.
But there's been nothing official, just Nick Harris's article. In that case, you'd expect a quoted company to put out an official announcement either confirming or rubbishing the article. The NYSE probably even requires it where's there's been a significant movement in the share price, yet there's been nothing whatsoever from united's board or their financial PR representatives. It's a rule that anything affecting the share price has to be announced via the market first.
The rumours of the suspension of the sale process could be true, or the Harris article could have been an attempt at market manipulation by short sellers of the stock. I hope the NYSE is demanding answers.