Forty years ago the ATLAS consortium (AF, LH, IB, Alitalia, and Sabena) pooled resources to maintain early widebody fleets. Most of ATLAS had bought the DC-10-30, although AF did not. Yet the AF shop performed heavy maintenance on the CF6-50 engine for the other consortium members.
Of course a year or two later AF started flying A300s - using the same powerplant package as the DC-10-30.