Currently, the only three engine aircrafts still flying today is the Lockheed L-1011 and the MD-11s/DC-10s.
Now, a lot of people on the aviation forums complained about the "ugliness" of this concept plane, but people really need to think first before speaking.
The diagram below is just a *ROUGH* sketch of the plane. What Airbus is interested in patenting is the tail design to hold the third engine.
The reason why aircraft manufacturers abandoned the three-engine design twenty years ago were due to noise, fuel efficiency, and difficulty of structural reinforcement especially along the aft/tail section for bearing the regular forces of the wind ALONG with the weight of an engine. Having a third engine mounted near the vertical stabilizer posed issues regarding hydraulic redundancy in the event that the third engine is massively destroyed. Take for example this famous DC-10 incident (United Airlines Flight 232):
A CG view of the incident, taken from Wikipedia. Original link here.
The Airbus "sketch" the the three engine configuration basically calls for a separation of the third engine from the main rudder, and replaces the vertical stabilizer with two redundant rudders on both ends of the horizontal stabilizers. This is of course, not a new design, and it has been used by Antonov, the modified Shuttle Carrier 747, and one of the old Avro prototypes.
Airbus claims that the tail design will not only reduce the noise, but will prevent a single point of catastrophic failure should the rear engine have issues. This sketch is NOT the actual aircraft that will be produced in the future, and those who declared this plane to be ugly doesn't realize that Airbus is trying to patent the aft configuration for a potential three engine jet, and not creating an actual plane (at the moment).
Today, we have quieter, more efficient engines, to the point where two-engine configuration is the norm for most aircrafts. However, I am not entirely convinced why we should bring back the trijets (as nostalgic as they are, I don't see them as economically feasible). Between the RJs, the VLJs, the 737/A319s to the jumbos, where will the trijets fit in?
