Mean NLTE corrections of the resonance Al I lines at 3944 Å and 3961 Å, colour-coded by log g: triangles are from Lind et al. (2022) and circles from Nordlander & Lind (2017). The corrections for individual stars from Baumueller & Gehren (1997) are shown with crosses (X), for four test cases of T_eff = 5200, 5500, 5780, and 6500 K; and log g=4.50, 3.50, 4.44, and 4.00. The error bars represent the standard deviation of the corrections of the two lines (often smaller than the depicted symbols). The hatched symbols indicate corrections that are based on one line.