Warning: Slight spoilers from Avengers: Endgame are ahead.
There are dozens of moments to scream over in Avengers: Endgame and Captain Marvel (Brie Larson) is the reason for at least two of them. The first is, of course, when she pops up at the beginning of the movie to save Tony Stark (Robert Downey, Jr.) from his death floating around in space (and then flies the ship down to earth using literally her bare hands like a boss).
The second happens shortly after that when, via hologram, Captain Marvel has a brand new haircut in Endgame: a short, almost pixie-cut style that immediately gets a lot of attention. Gone are Carol Danvers’ flowing golden locks; say hello to Captain Marvel who has very short hair and she means business. The other Avengers even make a joke about her new hairstyle, and while it is definitely something to talk about, it actually holds a much greater meaning to the character than just a brand new style choice for Endgame.
In the most recent comics, Carol Danvers' Endgame look is usually the short style she’s rocking as she fights bad guys on Earth and across all reaches of the universe. But like the movie version, Captain Marvel has rocked a few different styles over the years.
Captain Marvel first introduced in the comics is not the Captain Marvel we know today and actually went by the name “Ms. Marvel.” For this original run, Carol was based on writer Gloria Steinem, and Carol even worked at a publication called Woman Magazine under the direction of J. Jonah Jameson (who might be best known as Peter Parker’s boss). The most recent Captain Marvel writer (whose character is the inspiration for the movie), Kelly Sue DeConnick told Time, that this original Carol “Wore oversized glasses and blond, middle-parted hair and neck scarves. It was Gloria Steinem fan fiction in the most literal sense.”
But, like many Marvel characters, Captain Marvel went through different versions throughout the years. In 2012 she was essentially “rebooted” by DeConnick who gave her a military style look, leaned heavily into her role as a fighter pilot, and drew inspiration for the character from Chuck Yeager. This meant that Carol’s middle-parted hair had to go, replaced with the shorter look we see in Endgame. Carol shedding the hair on-screen is just the next step in her evolution of the character.
Back in Captain Marvel we even got a tiny taste regarding what hairstyles might come down the line, when in her green Starforce suit we see her wear a helmet with her hair sticking out of the top of it, a la a mohawk. This design was done by Jamie McKelvie, who helped re-launch the character for her new 2012 series; one of his initial drawings which “sweeps Carol’s hair into a pseudo-mohawk.” It’ll be so much easier for Carol to make it a real mohawk with short hair, even though she’s going to have competition for best Avengers mohawk with Hawkeye (Jeremey Renner).
Obviously, we don’t see Carol get her hair cut in the movie, because that would have only added to the three-hour runtime. But, since she appears first in the movie with long hair, and then “five years later” with short hair, we know it happens sometime in that time period. If Captain Marvel 2 (which hasn't officially been confirmed, but after the first movie's billion dollar payday, it's only a matter of time) takes place in the past, it will more than likely continue to feature a longer version of her locks, but we can always hope that Carol starts experimenting with hairstyles in the early 2001’s, or whenever the next movie takes place.