pterosaurs depends largely on weight, which has been controversial, and widely differing masses have been favored by different scientists. Some researchers have suggested that these animals employed slow, soaring flight, while others have concluded that their flight was fast and dynamic. In 2010, Donald Henderson argued that the mass of Q. northropi had been underestimated, even the highest estimates, and that it was too massive to have achieved powered flight. He estimated it in his 2010 paper as . Henderson argued that it may have been flightless. Other flight capability estimates have disagreed with Henderson's research, suggesting instead an animal superbly adapted to long-range, extended flight. In 2010, Mike Habib, a professor of biomechanics at Chatham University, and Mark Witton, a British paleontologist, undertook further investigation into the claims of flightlessness in large pterosaurs. After factoring wingspan, body weight, and aerodynamics, computer modeling led the two researchers to conclude that Q. northropi was capable of flight up to for 7 to 10 days at altitudes of . Habib further suggested a maximum flight range of for Q. northropi. Henderson's work was also further criticized by Witton and Habib in another study, which pointed out that although Henderson used excellent mass estimations, they were based on outdated pterosaur models, which caused Henderson's mass estimations to be more than double what Habib used in his estimations, and that anatomical study of Q. northropi and other big pterosaur forelimbs showed a higher degree of robustness than would be expected if they were purely quadrupedal. This study proposed that large pterosaurs most likely utilized a short burst of powered flight to then transition to thermal soaring. However, a study from 2022 suggests that they would only have flown occasionally and for short distances, like the Kori bustard (the world's heaviest bird that actively flies) and that they were not able to soar at all. Studies of Q. northropi and Q. lawsoni published in 2021 by Kevin Padian and colleagues instead suggested that Quetzalcoatlus was actually a powerful flier with a large breastbone to support the necessary muscles for creating the flight stroke and would probably have used its powerful hind legs to launch as high as when taking off, allowing it to gain enough height and momentum to begin the necessary downstrokes needed for takeoff. This same study also suggests that Quetzalcoatlus had limited walking motion in its wings, with the limbs on each