I have noticed that when I push the toilet flush button in a regular passenger airliner, it takes several seconds (perhaps 2 or 3) before the toilet actually flushes.
What is the reason for this delay?
Most passenger aircraft of today (747, A380, widebodies of any kind) use vacuum-flush toilets. It takes time for that system to go through. It also has to coordinate lids into the waste storage container that is usually fireproofed.
Those 2 seconds took decades to develop and keeps the odor and fires out!