  Indications of aluminium monoxide in atmospheres of exoplanets are being
reported. Studies using high-resolution spectroscopy should allow a strong
detection but require high accuracy laboratory data. A \textsc{marvel}
(measured active rotational-vibrational energy levels) analysis is performed
for the available spectroscopic data on $^{27}$Al$^{16}$O: 22\,473 validated
transitions are used to determine 6\,485 distinct energy levels. These
empirical energy levels are used to provide an improved, spectroscopically
accurate version of the ExoMol ATP line list for $^{27}$Al$^{16}$O; at the same
time the accuracy of the line lists for the isotopically-substituted species
$^{26}$Al$^{16}$O, $^{27}$Al$^{17}$O and $^{27}$Al$^{18}$O are improved by
correcting levels in line with the corrections used for $^{27}$Al$^{16}$O.
These line lists are available from the ExoMol database at
http://www.exomol.com.
