It is not normal for an airplane to fall, and much rarer still is that the airplane is never found, but sometimes it does.
It is relatively easy to find the list of missing planes on the Internet, but in cartodb they wanted to represent that list in the form of an interactive map.
Available at lfdodds.cartodb.com allows us to see the disappearances around the world, showing the year of the disappearance next to each of the points. You only need to hover over them to see the details, with the name of the company and the journey being made.
In red it is possible to see the last known case, that of the Malaysia Airlanes flight, where the plane with more than 200 passengers inside disappeared, an extremely high number of the flights we can find there.
In general, they are light aircraft, and small planes with less than 10 passengers, easy to get lost in the middle of the jungle or in the ocean, which is why the case of 2014 is so strange, mainly considering that the technology available now is very different from the one we had in the 50s-60s, when a large number of planes disappeared according to the same map.
If you want more information about this list, you can see it on this Wikipedia page, where it is possible to check how, effectively, the Malaysian flight is a record from the point of view of existing passengers inside the plane.