The current advice is not to contact Flybe if your booking is later than the next couple of days, as they need to deal with the most immediate first.
Looks as if everyone will be offered, without any extra cost, an alternative flight.
There may be some circumstances, however, when the times don't work for you, so I would suggest anyone in this situation contact Flybe (Manchester, London etc) or Manx2.com (Belfast) after 12 May, if they have not been in touch by then.
For travellers it's more of a pain than a disaster.. had the same problems a few years ago when Aer Arran stopped doing some of their flights and the other airlines flights didn't connect for me..aaargh.... but I got here eventaully!
Apparently several other smaller companies have gone in the last three weeks due to high fuel costs.