The intra-Europe flights operated by Delta (those that it had inherited when it acquired Pan Am's European ops in 1991) were expensive to operate, inefficient use of aircraft, and could not carry local traffic and therefore, were very big money loosers for Delta and the other US airlines that used to have an intra-Europe network. TW had flights from Paris to Geneva and Zurich, and at one point, operated flights from Zurich to Munich and Berlin, and from Rome to Athens, and from Athens to Cairo. It also had briefly a JFK-BRU-SVO flight. United did fly some of the intra-Europe flights from Heathrow that it acquired with Pan Am's LHR slots including LHR-MUC, LHR-FRA, LHR-AMS, and LHR-BRU. Only the AMS/BRU routes survived, until recently. American briefly had a ZRH-GVA leg added onto the JFK/ORD-ZRH route. Delta's intra-Europe flights operated with different a/c, not just the A310's. The 727-200's were used on some flights from Frankfurt to St. Petersburg, Bucharest, and other East European destinations. In the mid-1990's, before the JFK and ATL-IST routes were launched, DL had placed a 757 at FRA to operate the FRA-IST leg.
Delta sold the A310's it acquired from Pan Am to Fed-Ex and to other operators, opting for the B767-300ER as the workhorse of its transatlantic operations. Finally, the remaining intra-Europe flights Delta did operate in the 1990's were replaced by code-share services with a number of airlines, before the SkyTeam was created.