It’s rude and even strange in Japanese to say~たい (to want) directly about other people’s desires. That’s why there are constructions like たがる (seem to want).
There are many ways to avoid directly assuming たい of someone else, such as: ~たいだろう(と思う)、~たいみたい、~たそうだ etc.
Here, they are avoiding directly using ~たい about Narita Airport('s representatives) by informing that they say they want, whereas if they omitted という, they would be directly assuming what they want, which is just not a thing that happens in Japanese as far as I can tell.