Complex sentence: Former tenants of Concourse B include Continental Airlines and US Airways, who both relocated there in November 2009 after United reached an agreement with DIA to allow five gates at the western end of the concourse be used by its domestic Star Alliance partners.
Split into simpler sentences: Former tenants of Concourse B include Continental Airlines and US Airways. Both airlines relocated there in November 2009 after United reached an agreement with DIA to allocate five gates at the western end of the concourse for use by its domestic Star Alliance partners.