It was great to have an episode to focus on Twilight Sparkle and see more of her family. It is hard for fans too to not have high expectations in this regard. It is also easy for those that disliked "Marks and Recreation" (am one of those people, sorry) to expect an improvement with "Once Upon a Zeppelin" and that Iron Will would have a better episode here than Season 2's "Putting Your Hoof Down" (an example of a great character in an average episode).
The good news is that "Once Upon a Zeppelin" is a better, much better, episode than "Marks and Recreation". It was great to see Iron Will again and while he was actually more interesting in "Putting Your Hoof Down" this is a better episode than that. Do think however that a better job could have been done with Twilight's family and it is hard to not dislike it when Twilight is not well treated. While not a great episode, "Once Upon a Zeppelin" is definitely worth a look.
"Once Upon a Zeppelin" does have a lot of good things. The animation is bursting with colour and beautifully detailed, the fluidity suitably smooth. The music has both energy and atmosphere. All the voice acting is very good, especially from Tara Strong. One of her best moments being capturing very movingly the pain Twilight feels when she is angry. The dialogue on the most part has brains and heart, especially Cadance's dialogue and that in Iron Will's exit, and has a much better flow than the writing in "Marks and Recreation". Everything regarding being airsick thankfully doesn't become stale.
Some good storytelling can be seen here and enough of the character writing is great. Twilight's anger is intensely moving and one is completely on her side when it comes to the reasoning behind it. Iron Will has a priceless exit and the chemistry between Twilight and Cadance is sincerely done. Twilight is relatable and beautifully written here, while Flurry Heart is adorable and Cadance is a very sympathetic voice of reason. Iron Will is entertaining. The moral is not a near universal one but it is a relatable one for actually quite a number of people, being somebody who had an overworked mother for a while.
A better job however could have been done with Twilight's family in general, they come over as rather insensitive and selfish especially with the Northern Stars. Star Tracker is annoying and borderline creepy, reminded me of the times when in situations where people were over-familiar and remember how uncomfortable it made me feel. While Twilight's characterisation is spot on, the treatment of her is almost as cruel as with Fluttershy in "Putting Your Hoof Down".
While the airsick writing was fun, Shining Armor is too much of a wimp if to be more nit-picky. Also seeing as she wasn't in "Putting the Hoof Down", it does leave wondering how Twilight somehow seemed to know of Iron Will. That's not really addressed here.
Overall, not great but worth seeing. 6/10.