The mid-air sequence sees the rivals come to blows aboard a jet with Hugh Jackman and Nicholas Hoult. The scene also explains how McAvoy's Charles Xavier is able to walk in the film after becoming wheelchair-bound in First Class.
Days of Future Past, a follow-up to 2011's prequel, will unite the cast of the original trilogy - led by Patrick Stewart and Ian McKellen - with newer stars James McAvoy and Michael Fassbender.
Ellen Page, Halle Berry and Anna Paquin are among the other returning cast members.
The Bryan Singer-directed blockbuster will serve as a sequel to both X-Men: The Last Stand and First Class. Days of Future Past sees the X-Men fighting for survival across two time periods.
X-Men Days of Future Past: The making of Bryan Singer's superhero epic
The original trilogy's characters join forces with their younger selves in order to change their pasts, and thereby prevent a cataclysmic future.
The film is based on Chris Claremont and John Byrne's acclaimed '80s comic book run.
X-Men: Days of Future Past will be released on May 22.