I believe you are correct with 1988. BA was riding high. The following year it produced that ad which is considered one of the finest airline ads ever made.
Yes SAS flourished in the 1980s under Jan Carlzon.
Best business airline (the first carrier to provide business class lounges at all airports) in Europe, best punctuality, incredibly high load factors in business class on its Scandinavian routes and the first airline (in Europe) to put passenger-facing staff through a PPF programme.
It also one of the few, if not the only airline in Europe, not to levy a business class surcharge. SAS’ business class pricing didn’t go down well with Air France.
The latter insisted SAS charge more but it refused and as a result the French govt forced an SAS Paris-bound flight away from French airspace (the flight had to divert to Brussels) until the matter was resolved. This incident is reported in Jan Carlzon’s book “Moments of Truth.”
At peak times, it was not unknown for SAS to fill over 90 per cent of its DC-9/MD-80 accommodation with business class passengers on routes like London-Stockholm.