NEW YORK ( Reuters ) - Merger talks between United Airlines ( UAUA.O : Quote , Profile , Research ) and Continental Airlines Inc ( CAL.N : Quote , Profile , Research ) have picked up pace , but a deal still hinges on the outcome of discussions between Delta Air Lines ( DAL.N : Quote , Profile , Research ) and Northwest Airlines Corp ( NWA.N : Quote , Profile , Research ) , people briefed on the situation said on Friday .