United Airlines (UAL) CEO Smisek to Step Down; Successor Named
http://www.cnbc.com/2015/09/08/unite...ek-leaves.html
This quick of a replacement, with no successor in place (Munoz is a boardmember who's temporarily taking the lead) is a clear firing of Smisek.
Edit: sounds like Munoz will be a permanent replacement, not temporary. That indicates that the United Board of Directors had a 'succession plan' in place prior to implementing this.