I see that the upgradable buildings are no longer visible in the store (the shopping cart button).
The problem is that you can't see what additional items you need to complete the upgrade. This is a huge problem for new players that have not discovered the Wiki or this forum. Since they can start the upgrade and then only find out the additional items after its built. So that building will be useless till they find the additional items to complete the building.
which brings up one of my suggestion, show the additional items when you click the upgrade button.
http://airportcitygame.com/threads/display-additional-items-needed-when-upgrading.19085/
The problem is that you can't see what additional items you need to complete the upgrade. This is a huge problem for new players that have not discovered the Wiki or this forum. Since they can start the upgrade and then only find out the additional items after its built. So that building will be useless till they find the additional items to complete the building.
which brings up one of my suggestion, show the additional items when you click the upgrade button.
http://airportcitygame.com/threads/display-additional-items-needed-when-upgrading.19085/