LONDON ( Reuters ) - TUI Travel ( TT.L : Quote , Profile , Research , Stock Buzz ) , Europe 's biggest travel firm , said on Monday Thomas Cook ( TCG.L : Quote , Profile , Research , Stock Buzz ) has withdrawn from discussions with TUI Travel and Lufthansa ( LHAG.DE : Quote , Profile , Research , Stock Buzz ) about a merger of its charter airline Condor with TUIfly and Germanwings .