An image comparing the size between a human and bird Argentavis magnificens. Depicts Dr Kenneth E. Campbell at the National History Museum of Los Angeles (around 1980). Image source: wikipedia
The heaviest known flying bird, Argentavis magnificens (“magnificent Argentine bird”, or more literally “magnificent silver bird”), was more than twice the recently discovered Pelagornis’ weight but had a shorter wingspan. It had an estimated wing span of 5.09–6.07 m (16.7–19.9 ft), a height of circa 1.5–2 m (4.9–6.6 ft), and a mass of approximately 70–72 kg (154–159 lb).