I recall being at DTW a couple times back in the mid 1980s and seeing a Sabena 737-200 fly out of there. At the time I thought it was strange knowing that it probably could not fly DTW- Brussels even via JFK.
I later thought that perhaps Sabena based a 737 in the United States such as at JFK to serve the feeder routes similar to what Iberia does at Miami with the A320.
During this time though, Sabena was flying DC-10s and 747s to Detroit. I remember being at the airport one afternoon and seeing the 747 take off and head west like it was flying to Chicago, at the time I thought it was weird that a 747 would head west to Europe. Later on that evening the 747 returned to DTW so I am thinking that a 747 flew from Brussels to ORD with a stop off both ways at DTW.
Would the Sabena 737s at DTW be the case of a feeder service from Chicago or JFK?
There was another time, in the mid 1990s that I recall seeing an Aer Lingus 732 at DTW, was that another case of a feeder or was it possibly being leased by some charter company?