I wonder what those other 40% are? I guess it all depends on what the meaning of "speak of" is.
In October 21 1958, a group of castrist rebelds seize a DC-3 of Cubana de Aviación with 14 persons. The airship flew for the province of Oriente and was obliged to land in a trail dominated by the Guerrillas. According to the revolutionaries, with this hicjacking they want receive the attention of the United States Government, so that it did not send more weapons to the General Fulgencio Batista.
In November 1, 1958, the guerrillas hickjack another airship with 20 persons, in the route Miami - Havana - Varadero. This airplane Viscount-755 is diverted to Oriente near Holguín, and the hicjackers obliged the crew to landed in a trail of the United Fruit Company, near the Preston town. But cannot land in this trail by their reduced dimensions, they began to fly in circles in the night, they could not see the trail. When see that remained few fuel, they decided to land, erring the trail for 3 kilometers, and falling to the sea, in the Bay of Nipe. Dying 17 persons, and 3 passengers remained injured, but alive. The guerrillas asked excuses and indicated that their intention was that US did not deliver more weapons to the General Batista, besides they not were done responsible for the action of some isolated revolutionaries.
November 5, 1958, the guerrillas return to operate and hijacking a DC-3 of Cubana (flight 482), piloted by Assembling Pïedra, that flew the route Manzanillo to Holguín. There was 25 passengers and 3 crew. The airplane lands in the rebelds zone.
If you are speaking of only US hijackings why cite your source which gives global hijackings -when was the first US hijacking? Not in 1947.
As compared to dozens per year from 1968 to 1973, the total number for those years being 364. The numbers slacked off a bit after 1973 mostly due to (get this) an large increase in the number of armed air marshalls.
Wow. People with guns on airplanes makes flying safer. Who'da thunk it?
So, pre-1968 not that much to speak of. Some yes, but a drop in a bucket compared to post 1968.