The simulation of the B–X system of AlO (red line) is compared to the spectrum of VY CMa (blue line). The simulation was obtained for T_rot = 700 K and T_vib = 2200 K. A rescaled spectrum of Betelgeuse is also shown (grey line) to illustrate the contribution of photospheric (and circumstellar) features that have not been included in the simulation. From top to bottom, the panels contain sections of the spectrum dominated by the Δν = 2, 1, 0, and –1 sequences. The positions of AlO band-heads are indicated with red markers and labels (giving ν′′ and ν′), while some of the strongest features in the stellar spectra are indicated by grey markings.