Between May 2005 and March 2008 the CARIBIC container (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container; www.caribic-atmospheric.com) was deployed aboard a Lufthansa Airbus 340-600 passenger aircraft for 40 round-trip flights between Frankfurt, Germany to Manila, the Philippines with a stopover in Guangzhou, China. During these flights carbon monoxide (CO) and other atmospheric trace constituents were measured in the upper troposphere (UT) between South China and the Philippines. A total of 132 events having CO enhancements >10 ppb above background were observed in the UT over the region, 51 of which had enhancements >50 ppb. For these events enhancements ranged from 52.7 to 221.3 ppb and persisted for 3 to 78 minutes (~40 to 1200 km), indicating strong pollution from biomass/biofuel/fossil fuel burning on the trace gas composition of the UT. Back-trajectory analysis shows that South China, the Indochinese Peninsula, and the Philippines/Indonesia are the main source regions of the high CO events. The composition of air parcels originating from South China was found to be primarily influenced by anthropogenic urban/industrial emissions, while emissions from biomass/biofuel burning contributed substantially to CO enhancements from the Indochinese Peninsula. During the Philippines/Indonesia events, air mass composition suggests contributions from both biomass/biofuel burning and urban/industrial sources. Long range transport of air parcels from Northeast Asia and India also contributed to CO enhancements in the UT over the region. The general features of regional influence, typical cases, and the contributions of biomass/biofuel burning and anthropogenic emissions are presented and discussed to characterize the air parcels during the observed high CO events.