Which of these birds had the largest wingspan of any flying bird yet discovered?

Pelagornis sandersi is an extinct species of a flying bird, whose fossil remains date from 25 million years ago, during the Chattian age of the Oligocene. The sole specimen of P. sandersi has a wingspan estimated between 6.1 and 7.4 m (20 and 24 ft), giving it the largest wingspan of any flying bird yet discovered, twice that of the wandering albatross, which has the largest wingspan of any extant flying bird (up to 3.5 m (11 ft)).

In this regard, it supplants the previous record holder, the also extinct Argentavis magnificens. The skeletal wingspan (excluding feathers) of P. sandersi is estimated at 5.2 m (17 ft) while that of A. magnificens is estimated at 4 m (13 ft).

Some scientists expressed surprise at the idea that this species could fly at all, given that, at between 22 and 40 kg (48 and 88 lb), it would be considered too heavy by the predominant theory of the mechanism by which birds fly. Dan Ksepka of the National Evolutionary Synthesis Center in Durham, North Carolina, who discovered the new species, thinks it was able to fly in part because of its relatively small body and long wings, and because it, like the albatross, spent much of its time over the ocean.