About 20-odd years ago, I used to fly regularly between HLP ( Halim) and BDO ( Bandung).
This was before the new expressway was built, and a road trip would take about 3.5 hours.
Train service was not that good - and it was about 3 hours.
The route was served, as I recall, by both Merpati and Sempati.

At one point, one of these also operated SIN-BDO, which I loved, since it meant I could fly SIN-BDO-HLP//CGK-SIN, or reverse,
and not have to make the trip both ways between Jakarta and Bandung ( I did business in both cities).