In the meantime the Wright brothers had resumed their field practice. During the month of May, 1908, they tested their famous aëroplane of 1905, provided with increased engine power, and carrying two passengers upright. A few brief flights were made at speeds of 41 to 44 miles an hour, showing that all the mechanism was adequate and effective. But on May 14th a false push on a lever, made by Wilbur Wright, brought the flyer to earth, wrecking it too badly to be repaired in the few days available for experimentation. These flights were but preliminary to the official trials set for the approaching summer; for the brothers had contracted to furnish one machine to the United States Signal Corps, another to a French syndicate. The Chief Signal Officer of the United States Army in December, 1907, had issued specifications, and invited bids, for a flying machine apparently far in advance of the art. The flyer was to carry two men aggregating 350 pounds, was to remain aloft one hour continuously, and was to maintain an average speed of 40 miles an hour in a cross-country flight to and fro, covering a distance of ten miles. The contractor must instruct two officers to operate the flyer. Furthermore the machine must be capable of flying 125 miles without stopping. The requirements seemed severe, even to those well versed in aviation. Nevertheless two bids were received; one from the Wright brothers for a biplane to cost $25,000, another from Mr. A. M. Herring for a biplane costing $20,000. Both bids were accepted for the summer of 1908; but only the Wright contract was eventually carried out. About the same time the Dayton inventors had sold their patent rights in France to a syndicate in that country. The contract specified a machine for two passengers, having a speed of 50 kilometers an hour, and a range of 125 miles. Furthermore, the inventors agreed to instruct three pupils to manage the aëroplane. The fulfillment of these two contracts occupied some months, but presented no formidable difficulties. Though neither of the brothers had ever flown an hour, and though both were comparatively unskilled as operators, they had such faith in their invention that they undertook to launch themselves publicly in untried machines, Wilbur Wright in France, Orville in America, at about the same time.