WARNING: The following contains spoilers for Chapter #133 of Attack on Titan, "Sinners," by Hajime Isayama, Dezi Sienty and Alex Ko Ransom, now available in English from Kodansha.
As Attack on Titan fans -- and even those only casually acquainted with it -- know, Hajime Isayama's titular creatures come in all shapes and sizes. Some are so abnormal looking, in fact, that they cross over from horror to comedy. The series' Titan Shifters are far less laughable: as the powerhouses of Isayama's grim world, each of the Nine possesses unique abilities passed down through generations. Common among nearly all of them is a large size, but though some of them, the Colossal Titan, in particular, reach towering heights, none of their amazing powers have included the capability to lift off from the ground entirely.
This all changed when Falco Grice, one of the next generation of Marley's Warrior squad, inherited the Jaw Titan from Porco Galliard. When Falco first unleashed his new Titan form at the Paradis Island harbor battle, it was radically different from what came before: it had wings. Because Falco had almost no control over his new body, we didn't get to see if these wings were capable of achieving flight, or if they were just for show -- to match his avian name. But in Chapter #133, Falco gains an important insight into the Jaw Titan's history that could not only alter how the Titan is used but more specifically, how it can be used against Eren.
Presently, Falco, Gabi Braun and Annie Leonhart are heading away from Eren's rumbling on an Azumbito vessel. This weighs heavily on Annie's conscience, and she's horrified when the two children suddenly decide to take off. And, by take-off, they mean into the air. The shifters are not only passed on the powers of their Titan's previous holder but also some of their memories, too -- in the same way the Avatar cycle connects its title-holders together in The Last Airbender franchise. Falco tells Annie that he dreamed of "flying above the clouds," attributing the vision to his suspicion that a former Beast Titan must have been able to fly. He and Gabi theorize that because he gained the Jaw Titan by way of Zeke Jeager's spinal fluid, his form is much more animalistic than Porco's or Ymir's. This is comparable, Falco reasons, to how Annie's Female Titan can absorb other shifter abilities.
If successful in his goal to become airborne, this could change the entire battlefield of Attack on Titan's climax. With Mikasa, Armin, Levi and the others heading towards Eren in a plane, and the continent currently unleashing bombs on him from above, the sky is clearly the best vantage point to reach and possibly harm the ginormous Founding Titan and the scores of Wall Titans flanking it. While Eren's connection to his friends through the Coordinate Point keep them in his mind's eye, he may have turned a blind one to Gabi and Falco -- and he likely won't be expecting the Jaw Titan to have evolved wings, even if he does maintain a link to his half-brother.
Eren's enemies need all the advantages they can get right now, and if the series' overriding theme is anything to go by, it's usually the smallest and most underestimated of this world who do the most good.