In 1970, I was lucky to be in the right place at the right time, and with just exactly the right experience--having examined the London, Berlin and Maxberg specimens at various times during the preceding three years--and to my surprise, recognized that a fragmentary specimen displayed in a Dutch museum was not a pterosaur, as it was labeled, but actually was a fifth specimen of Archaeopteryx. The specimen consisted of two small counterpart slabs of limestone that had been found in a small quarry (now closed) north of Richstatt in 1855--six years before the discovery of the feather and the London specimen! (from Discovery, Vol. 11, no. 1, May 1975, pp. 15-23)In describing the specimen, the paper being published in 1972, Ostrom began to become increasingly interested in the bird-dinosaur relationship. Studying the specimens of Archaeopteryx and other dinosaurs like Deinonychus, Ostrom noted that there were many similarities between birds and dinosaurs and noted specifically that Archaeopteryx "obviously represent[s] an extremely early stage in bird evolution." In the same article Ostrom recognized that his renaming of the specimen had incited not only his own interest in flight, but also that of others.
Ostrom went on to study flight origins. He specifically questioned and compared the hypotheses of tree down and ground up flight models. For those not sure of what that means, refer to this image: