In this paper, the effect of weaving machine settings on weavability limits of air-jet looms was investigated by weaving plain weave fabrics with polyester warp and weft yarns. For this purpose, firstly, weavability limits were determined for 16.7 tex weft by setting back-rest height, total warp tension, frontshed angle and shed closing time at different levels without changing the properties of warp. For each machine setting, weft density was increased gradually until reaching the weavable limit. During the experiments, weaving continuity, unfavorable effects interrupting this continuity, negative changes on fabric and yarns were observed. In the mean time, the warp yarn tension and cloth-fell distance were measured. Later, the weaving with 7.8 and 33.3 tex wefts was carried out at the settings required to produce a weave at the maximum weft density for 16.7 tex weft. The maximum weavable weft densities were determined for these two weft yarns. Finally, the obtained maximum weft densities and cover factors with three different weft yarns were compared with the results obtained from theoretical equations of Pierce, Love and Brierley.