Continuity mistake: When Harry is narrating a letter to Padfoot, he sees a Thestral flying in the far distance, and it disappears behind a mountain. He hikes (presumably) all the way to where he thinks the Thestral went, and he finds Luna Lovegood in a clearing with a few Thestrals. For one thing, the Thestral that disappeared behind the mountain was MILES away, and it would have taken Harry a couple of hours, at least, to hike that distance through mountainous terrain. But, when he arrives at the clearing with the Thestrals, the daylight hasn't changed at all (should have been noticeably different lighting). Once he arrives there, he sees that even the largest Thestral is no bigger than a horse. But, when he first saw the Thestral disappear behind the mountain, at that distance the Thestral was about the size of a commercial jet airliner.
Charles Austin Miller
30th Jan 2017