Goofs

The relative sizes of monsters and aircraft change wildly during the film. Rodan can crush jet fighters with his feet because they are slightly larger than his toes. But when he's reaching toward the enormous flying ship Argo, which is giant compared to a mere jet, it is barely bigger than Rodan's feet. In the Antarctic scene, an Osprey helicopter is slightly larger than one of Ghidorah's heads. Later the Argo ship, which is so big that it can easily carry multiple Ospreys, is dwarfed by Ghidorah's heads.

As Ghidorah and Rodan fly toward each other, one shot shows Ghidorah with tendril-like "hair" on its three heads. The monster was actually designed with a kind of mane originally, but the mane was removed during production. They neglected to remove it from this particular shot.

When Madison is looking at the map of the Monarch bunkers worldwide, the only bunkers shown on or near the North American East coast appear to be Montreal, Boston, Washington, DC, and Atlanta. When the map is next shown, focused in on Bunker 09 in Boston, a bunker in Detroit is shown that was not on the previous map.

During the final clash in Boston, a continuous shot of Godzilla grabbing Ghidorah and hurling him away was cut in two and several reactions shots and expository dialogue from the human characters inserted in between. So when Godzilla begins swinging Ghidorah around, the film abruptly cuts to the humans watching the fight for several seconds, then when it cuts back to the monsters, they are in the exact same position and continuing the exact same movements as before, as if they had been frozen in time during the cutaway.

Submarines cannot use GPS for deep water navigation.

It was stated that Washington, DC was being hit by a category 6 hurricane. The Saffir-Simpson Hurricane Wind Scale only goes to category 5; no matter how strong, a hurricane couldn't be a category 6.

When the submarine is diving and hit by the impact, one of the orders shouted by the captain was "emergency blow". This is an order to use all relevant systems to immediately send the boat to the surface, breaching at a severe angle like a whale. This order is apparently ignored. An emergency blow does not take place until later, after the warhead goes off.

There are numerous instances where you see lava flowing under the water on the seabed floor, yet the water is unaffected and does not boil off into steam.

While at the site in Antarctica, Dr. Mark Russell is knocked backward from a close proximity explosion. The shock wave from this blast would have seriously injured him internally if it didn't kill him outright. As for him being knocked back, resulting in a collision with a large stationary object, the speed with which he was traveling at when stopped by the object would also have seriously injured or killed him.

Godzilla, Mothra, Rodan and the other Titans are classified under the genus "Titanus". In reality, the genus is reserved for a group of very closely related species (lions, tigers and leopards), so seeing arthropods, reptiles, mammals and cephalopods all lumped together into such a specific group makes no sense, however it could be interpreted as a code-name and not as a strict scientific name. Alternately, since all the Titans are functionally a single specimen species, one could postulate "Titanus" is a phylum, and Godzilla's "proper" scientific name is "Titanus gojira gojira gojira gojira gojira," being the single extant specimen of his Class, Order, Family, Genus, and Species. This still requires some extreme massaging of scientific nomenclature to work.

The idea that radiation can generate new growth in barren landscapes or lead to a resurgence in the populations of endangered species. While it is true that radiation can spur the evolutionary process by increasing DNA mutation rates, this is only feasible at fairly low rates of continuous exposure (such as a small percentage increase in UV rays due to ozone depletion). The kind of radiation that Godzilla and the other Titans pump out would only serve to give most ecosystems harmful acute radiation exposure, given that biological processes that run on radiation is dubious at best, it makes more sense, as the Titans absorbing "bad" radiation, processing it in their systems and excreting it as "helpful" waste radiation. It's also specifically stated that their radiation helps the growth of prehistoric vegetation, so maybe these happen to be flora species that were adapted to the activities and radiation of the Titans.

This movie states that Ghidorah is a fairly recent discovery thus Monarch has had little time to study him. Except that the post-credit scene in Kong: Skull Island (2017), set in 1973, shows that Monarch knows about him along with Godzilla, Rodan, and Mothra. However, this was simply a cave painting that offered a physical description of Ghidorah and not much else, Ghidorah himself was discovered by Monarch in 2016 frozen in ice.

Mothra is able to grow up and lay an egg within the span of two days. While one could argue that she had grown within the egg during the extended period of time that she was in the egg, this doesn't explain how she was able to create an egg within a day.

This is because she is a fictional monster and can do whatever the writers say within the created universe.

Dr. Ling is present on the Argo during Rodans emergence and Godzillas supposed death. The she is suddenly present at Mothras emergence from under the water fall, only to be on the Argo again when Mothra resurrects Godzilla.

Ilene Chen is the scientist present with the rest of the main cast throughout the movie. Her twin sister Ling is the one present during Mothra's metamorphosis. She is even credited for both roles on this site.

During the Senate hearing, the topic turns to the US military taking over Monarch's operations. However, the Monarch mothership is introduced as "USS Argo." The designation "United States Ship" is used solely for commissioned vessels in the United States Navy. Either the Argo and Monarch are already under US military jurisdiction and the Senator was unaware, or someone just likes "USS" a lot.

In the ancient undersea temple, there is an engraving of Godzilla, and next to it is its name in modern Japanese script.

On the touch screen guide to the locations of the Titans, the Titan in Australia is listed as being located at Ayers Rock. The name was officially changed to Uluru in 2002. The name comes from the Pitjantjatjara Anangu, the Aboriginal people of the area who are the traditional landowners of Uluru.

After arguing with her mother, Madison's mouth moves while she closes the radio room door, but nothing comes out. She has a line here in a deleted scene where her argument with Emma is slightly longer.

The oil derrick-covered dusty plains that Scylla emerges from are stated to be located in Sedona, Arizona, despite, actually resembling the oil-free red rock mountains of West Texas.

When there is a pan shot out of Fenway Park, you can see a US Navy destroyer on the Charles River. There is no way to get a ship that large all the way up the river to that area, as all of the bridges are too low, and the locks at the Museum of Science are too small.

Godzilla makes landfall from the Charles River. But one in-between shot shows him stepping out of the Boston Bay at the Financial District, several miles East, with the Monarch fleet in tow. (There's also the issue of Godzilla having to take a circuitous route to navigate the Charles, which is too shallow to accommodate a creature of his girth, instead of just stomping into town directly from the ocean.)

When attacking Ghidora, there is absolutely no reason for the attacking aircraft to fly so close to the monster as to be batted out of the air.

Throughout the film, supposed wolf expert Mark Russell keeps drawing comparisons between the behavior of real wolves and Titans to predict their behavior, particularly the theory that wolf packs are lead by an "alpha". This idea used to be popular in the mid-20th century to explain pack hierarchy and behavior among unrelated wolves in captivity, but it was disproved in the '90s after scientists began studying wolves in their natural habitat. Wild wolves do not actually have an "alpha" leading the pack, they bond around family relations with a dominant pair of parents who are periodically replaced by later generations. Mark studies wild wolves, so he should know this.

Stanton claims that Homo sapiens are carnivores. However, all hominids are omnivores.

Millie Bobby Brown is playing a character that appears to be 15-16 years old, but the movie shows flashbacks of her supposedly five years previously where she was no older than six at the most.