The possible retirement of the dear old VC10 as a people mover once again brings up the two man crewing debate. Technology has provided us with improved collision warning, better on board planning and all knowing receivers but it can not replace a sick or unable to cope co-pilot. I can think of a significant number of occasions when a co has just stopped functioning when under pressure and a rear crew member has had to provide back-up. Statistically, an insignificant event but not insignificant when it happens to you and definitely a flight safety hazard.