In that response, Irving is weak-manning Langewiesche's article, by attacking only the weakest, most speculative parts. As Argonaut says, it is mostly concerned

In that response, Irving is weak-manning Langewiesche's article, by attacking only the weakest, most speculative parts. As Argonaut says, it is mostly concerned with the point that Langewiesche is speculating about the captain's state of mind and motives. Irving makes no attempt to explain the inconvenient fact that someone activated the Inmarsat system and turned the airplane south an hour after it could have landed at Kota Bharu or Penang. In addition, Irving has no qualms over speculating when it seems to suit his purpose. He claims that the rational choice for someone wanting to disappear would be to head east, ignoring the fact that one has to go further in that direction to reach the open ocean while avoiding radar. Irving concludes by making an issue of the fact that the section of flap that washed up in Tanzania was not deployed at the time of impact, which is an utter non-sequitur. The thing is that once you have compelling technical evidence that the disappearance was not accidental, it is reasonable to speculate about motives, and the weakness of those speculations does not weaken the independent case that it was no accident.