Unable to land at Airport - is this a bug?

[Snowmantis]

With certain larger ship designs I have been unable to land at the airport of my capital city via the crew channel commands.  The spacecraft just bounces up and down in the upper atmosphere trying to land.

• I can pilot the ship down and land
  
• I can land on terrain and go to airport issue a command to land at "these" coordinates and all works just fine.   
  
• Smaller shuttle type ships, don't seem affected.  
  
• Using the same Airport blueprint in other cities I have not have any issue landing the larger ship at the airport.  
  

Is this some kind of landing check bug?   There are no objects in the way.  No vehicles, no NPCs, etc.  In fact an item I find interesting is that on another city with the same airport blueprint the raised landing pad is over the local villagers and their teepees and lands on that pad every time.
Is there something else I should be looking for?