If you ask me, the men in the Royal Family—in particular the Duke of Cambridge & the Duke of Sussex—have it fairly easy when it comes to dressing for an engagement or more formal event. They just have to wear the appropriate suit, tux, or other outfit & everyone thinks they look OK. But their wives are the ones who have to be more selective about what they wear because women’s fashion, accessories, hairstyles, & makeup are much more important things in society, for whatever reason, than men’s fashion is. Plus, they also have to be careful—or their protocol assistants do—to make sure that none of those choices will be considered culturally offensive in whatever country they’re visiting. Which is why it was very “safe” of Diana & Catherine, & their clothing assistants, to have their initial outfits be based on traditional Pakistani clothes. I’m assuming Catherine didn’t wear that the entire flight, considering how long it has to be from London, but that she excused herself & changed into it somewhere on the plane when they were about on approach for landing if not sooner (but not too soon).