Tour operators are obliged to have a travel bond because they are selling flights and accommodation to customers as a package. Where a travel agent goes out of business, the customer will have no idea as to whether or not the airline or the accommodation provider has been paid by the tour operator. This is where the tour operator's bond comes into effect. Your contract you see, is between you and the tour operator when you buy a package tour/holiday - not you and the actual service provider.
If you buy a package holiday and the airline goes out of business, it's still up to the tour operator to put the matter right.
Booking direct with an airline that goes out of business are a different matter. If you book direct with the airline - your contract exists with them alone. Airlines that operate in Ireland are licensed for business by the Commission for Aviation Regulation. Before a licence is issued they must submit detailed sets of accounts, budgets, business plans to the Commission, together with projected turnover, etc.
Furthermore, air carriers using aircraft registered in Ireland are also checked by the Irish Aviation Authority and separately, the Department of Transport.
Long-answer to short-question, airlines are not required to have any sort of a bond in place to cover customer travel in event they go out of business.
If you've booked those flights yourself, then you may seek redress of monies spent, through to the Small Claims Court, provided the cost is less than 1270 euro. If flight values are greater than this, you case goes to the Circuit Court. Given the airline you specify have gone into liquidation however, you may have to join the queue to get your money back.
I'd always advise anyone to obtain private travel insurance (either annual or single trip) before travelling anywhere. There are many policies available for a reasonable cost.
Hope this helps.