Risk management factors
Digitalis' post pointed out two very sensible points of view which appear to be at the poles of opinion. It is not possible to fly with no risk, but from what I can see there are many factors which influence the decision to fly again and there is not much in the way of the degree of risk attributed to each factor.
I cannot ascribe any degree of importance to the risk, corporate and political factors as this situation is unprecedented but the eventual situation is going to be a compromise between these factors. There may be others too.
1. Short term risk of an aircraft crashing. Probably one which flew into a heavy ash plume and flamed out.
2. Medium term damage leading to an aircraft accident. Possibly ash into engines and airframes degrading the performance of the aircraft.
3. Long term unserviceability of aircraft due to ash damage which require airframe replacement earlier than anticipated by business models.
4. Passenger confidence in the short term, possibly delineated by the ones wanting to desperately get home no matter what and those who will not get on an aircraft under any circumstances in the prevailing conditions.
5. Medium term passenger confidence. If a major fatality accident occurs which is attributable to ash then confidence will decline suddenly. It may also be affected by a near miss like Capt Moody's flight.
6. Financial pressures leading to a short term degradation of flight safety. WW may decide to get on an aircraft which may take off and land safely but this may not reflect operational conditions. There is no way on God's green earth that if the aircraft test flown so far had significant damage that this would be made known in the short term.
7. Political pressures in the short term may lead to degradation of flight safety. Especially in the UK with an election looming, it may be expedient to get stranded passengers home at some degree of risk.
8. Medium term financial pressures possibly a combination of the volcanic issues, plus fuel cost, plus banking problems, plus financial confidence in an airline may lead to risk taking.
9. The potential of the ash to cause damage is largely unquantified. It may be sharp and glassy but may have different characteristics to the other volcanic eruptions, but the analysis is going to take much longer than the allowances of the pressures listed above my give.
If the volcano continues to erupt at the current rate for a prolonged period (measured in weeks?) or there is a major eruption of another Icelandic volcano then all of the above will be exacerbated.
Let the train take the strain is my personal view.