Not a good article. He confuses subsidies with dumping.
Selling at a discount (or even at a big loss) is not dumping. Dumping is differential pricing between home market and foreign markets.
Did Boeing sold 787s to Air Canada at a steep discount vs. those sold to United? No. If anything United likely got a better deal.
Did Bombardier sold CSeries to Delta at a steep discount vs. those sold to Air Canada? Allegedly yes.