In his seven years as Chinese president, Hu Jintao has rarely looked more relaxed than on a 2006 visit to a Boeing plant near Seattle. Smiling broadly, he donned a baseball cap with the Boeing logo and gave a factory supervisor a hug.

If Mr Hu's speech leant towards the diplomatic – “Boeing's co-operation with China is a vivid example of mutually beneficial co- operation and win-win outcome” – the then Boeing chief executive Alan Mulally was more effusive. At the end of the public event, he pumped his fist and shouted: “China rocks!”

Since Richard Nixon restored diplomatic ties with China in the 1970s, Boeing has been at the crux of US-China relations. If Beijing has wanted to defuse criticism of its policies in the US, one of the preferred tactics has been to place a big order with the aerospace giant, which is the US's largest exporter to China.