(23 Jul 1997) English/Nat The merger of aerospace giants Boeing and McDonnell Douglas moved a step closer on Wednesday with the European Union withdrawing its opposition to the plan. Europe's endorsement of the 15 (b) billion dollar merger averts a potential trade war with the United States after last-minute concessions by Boeing and lobbying by the Clinton administration and Congress. At a crowded news conference in Washington, Boeing and McDonnell Douglas executives publicly welcomed the news