The idea of making the main character 'disappear'...

Picnic at Hanging Rock also comes to mind, with its central disappearance on a big rock, like the island in L'avventura. Still although that disappearance remains a mystery, it's rigorously examined and focused on, whereas L'avventura was radical for resolutely not caring about the procedural aspect.

Perhaps The Vanishing (1988) is an example as well? That film has an answer to its mystery - a sickening, unforgettable one.

Or what about Klute? Surely Alan Pakula and Gordon Willis were inspired by Antonioni and this film in particular, with the narrative putting the disappearance of Tom Gruneman on the backburner practically right after introducing it, mostly using it as an inroad to exploring a relationship.

Blue,

I understand your point about whether Anna really is the main character, and you quite correctly point out that over the course of the film Claudia is really the character who receives the most attention from the film.

But aside from your astute point that Anna serves as a frame of reference even after we no longer see her, it is true that until she disappears, she does act as the narrative's protagonist. Before returning to this point, I did want to say some things about the films mentioned here as well as some others not mentioned, where in general an unconventional approach to use of the protagonist is pursued.

Psycho. Although I consider myself a huge Hitchcock fan, it has been a number of years since I have seen this, but I do think that while the female lead obviously shifts from Janet Leigh's Marion Crane to Vera Miles's Lila, I think it is Perkins's Norman who is really the protagonist. But it is still worth considering Psycho in this discussion.

Rebecca. Another Hithcock film, albeit an earlier one, took what was really the novelist Daphne de Maurier's narrative to make a never appearing and in fact deceased character named Rebecca in a role that is central to the film. But it is probably better to see her continuing presence, lasting after her death, as more in the role of antagonist to the "I" character played by Joan Fontaine, who is the real protagonist.

To Live and Die in LA. This is in fact a fascinating comparitor to L'Avventura's narrative structure, and I have no doubt director William Friedkin had to have been strongly influenced by Antonioni. But there are differences, and I would argue that while L'Avventura is best understood as a narrative where the protagonist shifts from Anna to Claudia, in LA it is rather obscure who the real protagonist is. On a thematic level there arguably is no protagonist, with the characters more pushed along by the inexorable course of events, with unforeseen consequences altering their individual fates more than their supposed effective, but in fact ineffective, intentions, which are ultimately seen as illusory. But on a more conventional level the narrative arc of LA shifts protagonists at least twice, from the early suggestion it is Jim Hart, to Chance, to Vukovich. But what about Masters? Those who have seen LA I think understand this discussion.

The Thin Red Line. I consider this work by Terence Malick to be a masterpiece, but I also think many in the audience found its lack of a conventional protagonist to be confusing and even off putting. In its narrative structure TTRL in effect uses an ensemble approach to moving the narrative forward, with no central figure. But thematically one could argue that in fact it is Nature itself, or more accurately the duality of Nature, and Nature's relation to God, that is the protagonist. Concededly that observation is thematic and is not apparent on the film's surface as it were. And as pertains to this discussion it is perhaps a film that has even less in common with L'Avventura than some others. But I would expect Malick in fact had L'Avventura somewhat in mind in coming up with TTRL's very unusual approach to the role of the protagonist in the film's narrative.

No Country for Old Men. For a winner of the Best Film Oscar, this may be the winner that most confuses audiences in its choice of the role of protagonist. The marketing materials for this film notably took the position that there were three main characters in the film, Tommy Lee Jones, Javier Bardem and Josh Brolin. But then the Academy chose to award Bardem an Oscar in the supporting actor category. Not that such choice is controlling on this discussion, obviously. In any event his role of Anton Chigurh is more properly viewed as an antagonist, and not protagonist. But then who is the protagonist? If one were to come into the film when Brolin's character first appears, you would tend to conclude it is his character of Llewelyn Moss. As many people do so conclude. But then a point comes in the film very similar to To Live and Die in LA where one simply cannot hold to that view. My own view is that Jones's character of Ed Tom Bell is and has been all along the real protagonist, but one must concede that at least through use of a narrative's employment of a story within the story, the Moss character looks very much like a protagonist. I do think this choice by the Coen brothers is attributed by some to Cormac MacCarthy's story, NCFOM being an adaptation. But the protrayal certainly calls L'Avventura to mind, whether the Coens were or were not consciously influenced by it. Unlike Anna, Ed Tom does reappear, more than once, after it seems that the story has shifted to Moss. But he also acts as a more verbal Greek chorus, compared to Anna's silent "presence".

Persona. Bergman's masterpiece I think is the film most clearly influenced by l'Avventura, although I also think it may have been an unconscious influence. Likely was. There is no doubt Bergman saw Antonioni's films. He commented upon them, not always favorably. In fact a quote of his specifically dismisses L'Avventura, which in its own way is fascinating. (I happen to be a huge fan of Bergman's, but obviously disagree with him here!) Yet it should be obvious Bergman's dismissal of L'Avventura does not rule out that it may have influenced him, as no doubt imo it did. Persona is his own work, and obviously revolves around two main, and female, characters. Some significant percentage of viewers take the position, mistaken in my view, that the characters are in some way really the same person, or two sides of one psyche - how this is seen as the case is not here directly relevant. But in terms of Persona's narrative structure, it does raise the question who is the protagonist, whether Liv Ullmann's Elizabeth, or Bibi Andersson's Alma. In fact I think it is Bergman's genius that leaves that question without a clear answer. Even taking into account that Anna is verbose and Elizabeth nearly completely silent does not indicate an answer. So, one might say that the shift in the protagonist found in L'Avventura is not really paralleled in Persona, since Elizabeth and Alma remain together for nearly the entire portion of the film devoted to narrative explication. But arguably Persona is not that different, merely having the role of protagonist shift back and forth rather than make a single shift. And beyond that the role of Elizabeth can be seen as a silent Greek chorus to Alma's words and actions, which of course has parallels to Anna's silent role as L'Avventura proceeds, albeit with the distinction that Anna is not physically present.

Klute. I merely want to say I agree with the observation made above that Pakula probably had l'Avventura in mind in the choice of narrative used in Klute.

La Notte. While a different film from the one that precedes it, Antonioni himself arguably continued an unconventional narrative here as well (not to mention in L'Eclisse, although concededly that film has even less parallels than La Notte does). While Monica Vitti's role in La Notte of Valentina is arguably in clear support of Jeanne Moreau's excellent portrayal as Lidia, the film does seem to shift to Valentina for a rather lengthy period in unfolding the narrative. Still on balance the larger observation can be asserted that it is really Marcello Mastroianni's character of Giovanni who is the real protagonist. But, I would argue that is far from clear, and that La Notte has more in common with L'Avventura's approach to narrative than it does to conventional narratives.

I am sure there are other films that could be submitted for comparison, such as Mulholland Drive, but I will not discuss that one since i do not like it. But there are others still.

But returning to Blue's point, and as I think I have alluded to in discussing other films, the narrative of L'Avventura can best be understood as one where the protagonist shifts from Anna to Claudia.