By this time United States Lines, which had interested IMM, had been sold and contractually obligated to run "Leviathan" for a minimum of five return voyages on the Atlantic run per year. The Gibbs Brothers Inc would run her for her first voyages and train the crew until ownership officially changed hands. She immediately proved popular with the American public in the '20s, starting her career fully booked for her maiden voyage departing on 4 July 1923. Her passenger average reached a strong 1,300 by 1926, making her the #1 traveled ship on the Atlantic, but given her capacity of 3,000 it was too little to be profitable.