Hrm, you seem to be missing a few things here. It wasn't deus ex machina because 1. We knew about it before hand. There is no "Surprise, we have air defenses!" 2. Parson had the ability to use it and chose not to. Main Characters have no control over deus ex machina events. 3. It was NOT their biggest threat. You don't conserve firepower for the biggest threat and allow yourself to get buzzed. In fact, it was not a threat at all since Jillian didn't plan on fighting. But Parson didn't know that. But he could still look at Jillian's forces and judge that they were "not the main attack." Which means there is another air capable force out there that is even stronger than Jillian's.