There is a huge logistical dilemma to resolve when systems suddenly go down.
You need to remember that manual check in is not simply a case of scribbling out a boarding pass and writing a bag tag.
Weights need to be recorded of bags on a handwritten loads sheet, the name of each pax has to be written down with its catagory (male, female, child, infant etc) and ticked off a sheetwith a sequence number and if a seatplan is to be used then only two or three desks can be open for an individual flight (and lets face it thats not enough for Virgins rather high density jumbos) so that the seat plan sheet wont go missing. Someone needs to do all the calculations of weight alone as the load sheets arrive at the last minute. Not to mention all the passengers who may have checked in the night before when the systems were working or earlier in the day before the systems crashed. All these pax would have to be brought back and re-checked in as their info would be lost in a crashed computer otherwise.
Now if this all happens to one flight, expect a delay, but when it happens to the whole days operation then you have MAJOR problems on your hands! This is obviously what happened to Virgin on this day and credit should be given to the fact that they still managed to get loads of their flights out. All though I appreciate that this is of no comfort to small pilot.
Many moons ago we had a major computer failure to the Aer Lingus Astral system in dublin,cork, Shannon and Heathrow simultaniously. I cant speak for the other stations but in dublin we suddenly jumped into manual action (it was also about 10am so you can imagine the havoc that would occur). We managed to get the europeans out relatively on time by zoning pairs of desks to each flight and we went free seating onboard. The desks were closed at -25 (well, more or less!!! LOL) and the check in staff rushed the load sheets to the gate where those who already had a boarding pass from before the computer crash were then checked in by the gate staff and the despatcher did all the calculation work there and then. It really was amazing to watch how well it worked in the end. Unfortunately the longhauls were not so lucky and there were many problems there but merely due to the nature of the operation!!!!