The fact that the airline has sent out a strong message to the contrary as well as continuing flights should calm the situation to some extent. Furthermore, it should be pointed out that the airline made a profit last year showing that it is in a position of relative strength. The idea that one of the third party tour operators who buy seats on Monarch flights being the problem seems more likely, as has been pointed out. However, the loss of any of the tour operators working with the airline will obviously have a very immediate impact on revenue.
Additionally, I have long since had my suspicions about the parent company. Earlier this year, they put the "M" brand into administration having run it into the ground with the safety net of the guaranteed rent condition on the sale contract. Furthermore, they openly stated they were looking for investment and a buyer for Monarch having hired Deutsche Bank to "Explore Strategic Opportunities". In any other world, when a business openly states they require £35m of investment, it is not normally good news. Greybull also has a recent history of buying up other ailing companies for a nominal fee with little risk, stripping the assets and then placing them into administration when no buyer is forthcoming. Think about the hangar situation at MAN....
Then there is the completely unfathomable decision to completely replace the entire fleet with brand new aircraft which would suggest that, on the face of it, the business is in a good place and there is a good plan for the future. Looking at it cynically, one could say that, until the planes are built and in the air in Monarch colours, it is just the number 30 on a form. This might look good to a potential buyer or investor but it just doesn't make sense to commit an airline with a rocky recent financial performance to a multi billion pound order - one that would also require a full crew retraining/overhaul. Surely the sensible thing would be to consolidate and offer growth where appropriate and order new aircraft after a prolonged period of financial stability.
I'm sure the truth about the situation will out shortly and I hope that it is not bad news for the airline but enough people have seen and heard enough information to be extremely concerned.