[UPDATE, Jan. 19, 2017: United for this year added baggage handling and carbon emissions to its performance guarantee for corporate clients. Delta also now includes baggage handling in its service commitment but United said its environmental component is an industry first. If United's 2017 carbon emissions per available seat mile isn't lower than both American's and Delta's, it will pay corporate accounts based on their individual United carbon footprints. United is using data reported by each airline's Carbon Disclosure Project response or CSR report. For 2015, United said its carbon dioxide equivalent . . .