I've dug out the NYT article from Dec 89
KL867
This incident happened despite the KL crew knowing there was an ash-cloud in the vicinity, but
Mr. Steucke said yesterday that the KLM crew members had reported after landing in Anchorage that they had been unable to see the volcanic cloud and that it did not show up on radar.
There's also a mention of the BA and SQ incidents here.
Edited to Add. There is also this comment:
He said that the agency knew of three airlines - Alaska, Markair and Delta - that had halted operations into Anchorage but that it was up to individual operators to decide what to do about the alerts.
That's how it was in 1989, thankfully we no longer leave it up to the individual airlines ...