Moreover, both sides agreed to continue dual designation, i.e. designating two UK flag carriers as well as two US flag carriers, on the London–New York and London–Los Angeles routes. The principle of dual designation was extended to another two high-volume routes. The UK side chose to designate a second carrier on London–Miami, while the US side chose London–Boston for the same purpose. This meant that a second British airline was permitted to commence scheduled services on the former route, whereas another American carrier could do the same on the latter route. The UK government chose to designate Laker Airways as the second UK flag carrier on the Los Angeles and Miami routes, whilst the US government decided to designate Northwest as the second US flag carrier on London–Boston. (Pan Am and TWA continued in their role as the two designated US flag carriers between London and New York as well as London and Los Angeles respectively.)