United Airlines Holdings Inc. UAL, -0.31% said Tuesday it is launching the biggest transatlantic expansion in its history with 30 new or resumed flights coming from mid-April through early June. "We have long anticipated a strong demand recovery, evidenced by our large, strategic expansion in Europe, and with these new flights, we're proud to offer our customers more options and access than ever before," said Patrick Quayle, senior vice president of international network and alliances at United.