In that time up to 400 people will board and disembark 10-20 times. Guess what? Some things will break. I know I really only mention Boeings in this website, that is primarily because I have never flown an Airbus. However talking with pilots that do around the world the philosophy of Boeing and Airbus is the same. Both aircraft manufacturers build in redundancy protection for vital systems. That is planes have the ability to keep flying with something broken. For example on the B747 there are three air conditioning systems. If two failed in flight you as a passenger would not notice anything. However, when the plane lands it would not be allowed to depart unless at least two systems were functioning normally.

When things go wrong in the airline industry, they really go wrong. An engineering delay that cannot be estimated how long it will take, really is a nuisance. No one likes the situation. The engineers will tell the Captain it might take an hour to fix something, this will be relayed to the customers. Then the delay rolls hour after hour.
Passengers will ask "does anyone know what is going on?" That is a reasonable question. Please realise that modern planes are highly complex and some repairs just cannot be time-estimated accurately. For example, I had a delay where a wire from an engine that carried oil quantity information to my cockpit display was not working properly. The total length of wire in a B747, I am lead to believe, would reach the moon.

When I arrived at the plane the engineers had been trying to find the fault for four hours and had isolated the problem to somewhere in the forward hold area. It was like trying to find a needle in a haystack! I told my passengers that it could take anywhere from an hour to maybe at worst we would not travel. The best we could do was give the passengers a regular update. My wonderful company engineers did find and fix the problem in a little over 90 minutesf and we departed. This did inconvenience passengers, however they did arrive safely at their destination.

You will enjoy your flight better and arrive more relaxed if you accept that you are going to be late and there is nothing you can do about it. Safety is more important than schedule! 

When things go really wrong and you have to overnight stop you are going to be really annoyed because no airline is really capable of organising immediate hotel accommodation or transportation. It will take a couple of hours to do so.

The problems multiply if the cause for your overnight stop is weather related, for example a snow storm. Every airline will be in the same situation desperately pleading with hotels for spare rooms, pleading with bus companies for buses.

Hotels and bus companies just do not keep spare rooms or buses in case of an airline delay.

Then you have the problem with large aircraft of trying to keep passengers reasonably close to each other for ease of transportation and communication.

You should expect First Class passengers to be booked into a better hotel than Business Class passengers and same again for Economy or Coach class passengers. Economy class passengers are equally as important to airlines, but First Class fares are significantly higher than Business Class which is in turn higher than Economy.

What you pay is what you get! Fact of life.

Do not waste your time and upset yourself even more by demanding an unrealistic hotel upgrade.

An overnight stop is a recipe for a disaster. No-one wants this situation, but sometimes they occur. I think in 33 years I have had four. The problems are made worse when they occur very late at night, for example being the last flight, because there will only be skeleton staff available to handle you.

Imagine what it must be like if your plane has to return to the gate with a problem that will require an overnight stop and there are only four ground staff remaining at the airport. The rest headed home as soon as your plane pushed back from the terminal.

400 passengers will be angry and grumpy (rightly so!).

It will take two hours minimum for the staff to find hotel rooms and organise buses, maybe longer.