Some development of the navigation occurred. In 1744, the undertakers bought some land at Airmyn, and developed warehousing and wharfage there, as a more convenient point than Rawcliffe, where the water was shallower. In the 1760s, £13,000 was spent on improvements and maintenance, with several weirs being rebuilt to improve the depth of water. There was a long-running dispute with Arthur Ingram, who owned Knottingley mill, which started in 1731, and was not finally resolved until 1776, when the company bought both of Ingram's mills. Despite this, the general profitability of the navigation led the undertakers to be complacent about its development. They asked John Smeaton to suggest improvements in 1771, but the subsequent attempt to authorise such improvements was disputed in Parliament on the basis that the present navigation was totally inadequate. The recently finished Calder and Hebble Navigation proposed to build a canal from Wakefield to the Dutch River, which would bypass the Calder completely, and the Leeds and Liverpool Canal supported a Leeds to Selby canal, which would bypass the Aire. During 1772, they asked Smeaton to survey a route to avoid the lower Aire, but his assistant, William Jessop actually carried out the work. He proposed a canal from Haddlesey lock to the Ouse at Newland. With Parliament not reaching a decision, they reworked their plan, which was now for a canal from Haddlesey to Selby, with a new cut from Ferrybridge to Beal, and improvements above Castleford. In 1774 the Leeds to Selby bill was rejected by Parliament, but the Aire and Calder bill was passed, with a few amendments.