How do I identify airports with gates for Heavy aircraft such as the B787 or B747?

Hi @TheFakeCake1374, & welcome to the forums :slightly_smiling_face:

Virtually all airports in MSFS are procedurally-created. Only a very few are hand-crafted. The procedurally-created airports are only as good as the available data for each airport. Have a look at this post:

and @CharlieFox00’s post that I referenced.