Despite its huge wings and flight feathers, it is speculated that magnificens was unable to truly fly. It weighed around 150lbs, making it difficult to take off. Instead, the birds most likely had to run downhill into a headwind, which would then lift them up and allow them to glide. Gliding is a trait common in many modern species of raptor, especially the condor, who have the some of the largest wingspans of any living birds and are excellent soarers. The estimated glide speed for magnificens is 67kph (or about 41mph for those who are metrically challenged like I am.) Their estimated dive speed is 241kph. (150mph)
|Image from Playpen|
Edit (9-19-10) For another really awesome gigantic bird, check out the newly discovered Pelagornis chilensis!