Feel strongly about these letters, or any other aspects of the news? Share your views by emailing us your Letter to the Editor at letters@scmp.com or filling in this Google form . Submissions should not exceed 400 words, and must include your full name and address, plus a phone number for verification. In recent weeks, the skies of North America have been visited by a series of unidentified flying objects, and at least one high-altitude balloon from China. That balloon, which entered US airspace and was shot down by a US F-22 fighter jet in early February, caused a media frenzy and triggered a huge diplomatic issue between the two countries. In the following days, at least three other objects – of unknown typology and origin – were detected near, or above North America, with one of them flying over Canadian airspace. I would like to offer a critique of the exaggerated US response to the Chinese balloon, and to address how the response to the flying object over Canadian airspace reflects Canada’s dependence on the US military. That object, described as cylindrical in shape, was flying at an altitude of 40,000 feet, which Canada’s defence minister said posed a risk to civilian air traffic. Canadian Prime Minister Justin Trudeau ordered the take-down of the object, which was shot down by a US F-22 fighter jet. This reveals a certain power dynamic between Canada and the US. The object was flying over Canadian territory so one would have expected the Canadian air force to intercept it. Of course, the approach adopted is well within the remit of the combined organisation of the two countries, the North American Aerospace Defence Command, but that agreement offers the United States a position of responsibility over Canada. This kind of dynamic between a Nato member and the United States is not new. Apart from nuclear countries, such as France and Britain, the militaries of other Nato member countries are very dependent on US capabilities to operate properly. Roberto Santos, Belas, Portugal Don’t ignore population’s impact on environment I refer to the letter , “Shrinking population of China is no boon” (February 23). This encapsulates exactly the mindset which has helped to place the world in its present precarious situation. Your correspondents contend that baby bonuses are not generous in China, that congestion can be solved by spending more money on infrastructure, that population decline will undermine economic prosperity, reduce competitiveness and decrease demand for goods and services. They did not mention the polluted air, seas, lakes and rivers filled with garbage globally, and the shortages of food and water. Today’s Earth is already struggling to support its present population. Trevor Hughes, Pok Fu Lam