I saw on YouTube a helicopter carrying an airplane.
Is this possible, I mean is the maximum load compatible with the mass of this aircraft?
If you look more closely, this "airplane" is only the husk of a Tupolev Tu-134, a rather small airliner, and the helicopter is a Mil-26, the heaviest helicopter ever to go into production. Not only are the empennage and the outer wings missing, but also the engines, which helps to reduce the load considerably.
Mil-26 lifting a Tu-134 carcass, seen from below (source)
The empty weight of a flightworthy Tu-134 is 28 tons, but the engines alone weigh 2.3 tons each. Now remove the outer wing, empennage and cabin interior, and the remaining weight is within the 20 ton load limit of the Mil-26.
In Vietnam it was pretty common to remove crashed aircraft from the jungle using helicopters.
http://www.angelfire.com/mo/242sdASHC/213th.html gives a first hand account of a crewman flying quite a few of these dangerous missions.
http://www.combatreform.org/CH53AliftsA1andA4.jpg shows an A-1 and an A-4 being lifted by CH-53s, but larger aircraft like F-4s and F-105s were similarly airlifted out of the jungle to prevent them from falling into enemy hands.
As said, the aircraft is tripped of heavy equipment. The airframe itself is as light as possible to maximize cargo carrying capacity. And on separate note the video title is a bit provocative. The airliner is not big and even so it isn't in operational condition. Not really #MindBlown as the title proclaims.
This is all within limits of the helicopter's capacity, but we don't see such deliveries quite often. Think about carrying such cargo in strong winds. Road/rail/sea transport of airframes is still preferable to helicopter transport when safety is a concern. And when dismantling aircraft it's a good practice to use boneyards where everything from storage to scrapping is done so that there is no need to transport airframes around.