We report Ti concentration measurements in dilute AlTi alloys, acquired from direct analysis of the molten metal by laser-induced breakdown spectroscopy (LIBS). The LIBS analysis showed approximately constant Ti concentrations at melt temperatures above the liquidus, while at lower temperatures the measured concentration followed the L/(L + Al3Ti) liquidus of the phase diagram, confirming that the LIBS measurement accurately detects the dissolved Ti concentration in the melt. The LIBS measurements furthermore demonstrated that the Al3Ti phase forms or dissolves within minutes when the melt temperature is decreased or increased, respectively. For the first time, the liquidus line at low Ti concentrations in the AlTi phase diagram has thus been mapped using LIBS analysis instead of the more conventional but time-consuming thermal analysis methods. We conclude that LIBS analysis of molten metal offers a unique opportunity to monitor accurately the chemical composition of the liquid phase and reveal the formation of solid precipitates in real time.