Two stopovers in China, airline says I need a transit visa - why?

Am Australian, travelling from Europe to Australia via China. Schedule change initiatied by airline means I now have to stop in Beijing (1 hr) and Guangzhou (4 hrs) instead of just Guangzhou for 4 hrs as per original schedule. The airline tells me I need a transit visa. Why is this? I do not plan to leave the transit area of the airport in either Beijing or Guangzhou. x