Here's the short record of the BA flight that ran into the Mt Galunggung volcanic ash cloud in Indonesia on 24th June 1982. All four engines were restarted, but one was shut down as a precautionary measure due to surging.
It's not mentioned in this abbreviated report, that severe ash particle-blasting of the cockpit glass rendered forward vision practically impossible, thus increasing crew stress levels.
The crew were unaware of the eruption due to the eruption information not being relayed to them, and they didn't see the ash cloud due to darkness.
There's no doubt, the lessons learnt from the BA incident are being applied today, with a great deal of safety margin in mind.
ASN Aircraft accident Boeing 747-236B G-BDXH Jakarta