Major check-in problems at Manchester, UK, 13-6
 

There were long delays checking in at Manchester due to a computer breakdown today.

Flight delays after Manchester Airport check-in fails - BBC News

It's not quite clear from the BBC story (to me anyway) whether this is a failure of Thomas Cook's own system or the airport's generic multi-airline check-in system, if there is such a thing. It sounds more like a Thomas Cook failure with knock-on to other airlines.

Either way, the failure seems to be for a different cause than BA's the other day, but the effect is the same: chaos, queues, long delays. IMHO airlines and airports and handling agents have to improve their game. They have to get their minds round the fact that although failures are rare, when those failures do occur the impact is enormous for their customers. (I know that some here think that airlines aren't worried if they massively disrupt their customers' lives every now and then, and you may be right.) They have to get effective fallback in place. If manual check-in is no longer possible – and it probably isn't possible, for lots of reasons, especially for flights to the US – then they need effective crisis management. Extra staff who can be called instantly (or diverted from other tasks) if necessary to deal with the crowds, effective and prompt public and internal communication, top people ready to drop everything and get on-site to deal with media while also dealing with the crisis.
In your dreams, you say? Perhaps you're right about that too.