Continuity mistake: Near the beginning of the film where Howard Hughes flight tests the silver monoplane (the H-1), the close up shots show an open cockpit while the longer shots show a closed cockpit.
Continuity mistake: In the dining scene where Howard Hughes' girlfriend has a sundae sitting in front of her, the cherry which is on top of the sundae changes positions in several different shots. First, the stem is turned towards the left, a few shots later, it is turned towards the right, then left again. It also shows up in the bottom of the dish, then in the next shot, it is back on top of the sundae.
Continuity mistake: When Hughes and Odie are talking about mounting a camera on a biplane and removing one of the wings, the shots alternate between a back view of their heads and a front view of their faces. Odie's head position has no relationship to the one it had in the preceding angle in most of the cuts.
Continuity mistake: Immediately after the screening of "Hell's Angels", Noah Dietrich (seated right behind Hughes) begins applauding, and others join in. In the next shot of Dietrich, he begins applauding again.
Continuity mistake: While having dinner at Kate's house, Howard Hughes yells out a comment about money, and after that the roses on the table have totally changed position from before.
Continuity mistake: Hughes asks Ava Gardner "Feel like going to Paris?", then the guy behind her disappears.
Continuity mistake: In the final scene of the movie, as Hughes walks forward with Gardner, they stop walking in the head on shot. When the shot changes to a side profile, they are still walking forward.
Continuity mistake: When Howard asks L.B. Mayer to loan two cameras, we first see Mayer and his associates from Howard's viewpoint as he is approaching them, and Mayer is standing with the bar on his left. In the next shot Howard greets him, and the men in the group have changed places, with Mayer now facing the other direction and now the bar is on his right.
Continuity mistake: When HH's plane is rampaging the houses, a couple of white mugs in a kitchen fall down twice.
Continuity mistake: Hughes leaves Ava and goes, hat in hand, to talk with his two pals. Suddenly he is seen with his hat on. Less than half a second to put on a hat without moving your arm IS fast.
Continuity mistake: When Hughes is dining with Domergue and Juan Trippe is leaving the place, the spoon on the sundae keeps moving around.
Continuity mistake: Inside the projection room, Hughes hand the photo of an actress with a sketch of the Hercules behind. The sketch is sideways as we can see when the guy is flipping the photo. But when the angle changes finishing his movement, the sketch is seen straight.
Continuity mistake: During lunch with the Senator, the vegetables and potatoes on Hughes' fish change between the first and second shot.
Continuity mistake: After Howard Hughes says "Those sons a b**ches in Houston," the people in the background disappear.
Continuity mistake: When Ava Gardner smacks Hughes he falls down, knocking some flowers down to the floor, covering part of the first brick of the fireplace. When the shot changes, the brick is immaculate and the flowers are nowhere to be seen.
Continuity mistake: When Hughes is about to fly (and burn) in the plane, the plane is standing on a very long and straight runway. The shot cuts to Hughes inside the cockpit, and the runway behind him is a curve turning left.
Continuity mistake: When Hughes is asking Ava about going to Paris, 2 guys with blue suits pass behind three times.
Continuity mistake: Before Flynn is thrown the paper ball, a couple passes behind him and disappears in the next shot.
Continuity mistake: When Howard Hughes is having a shave with Katharine Hepburn, he has shaving foam left on his chin from the shave. In the next shot when Hughes goes to wash his face, all the foam has disappeared.
Continuity mistake: The amount of fog during the Hercules presentation changes abruptly in barely half a second.
Answer: The first sections of the film are shot in two-strip and three-strip technicolor, a common practice in the early versions of color filmmaking that were happening at the time. The scene on the golf course between Howard and Kate Hepburn is a prime example. As far as the later sections of the film, never underestimate the power of digital effects. :)