I did some user-testing for my Seatback Airplane Ordering System and got some very interesting feedback. I did this with 5 people and here are some of the things they pointed out:

Negative…

•  In the Coke screen, the ice/no ice can/no can options were confusing.
• When you add item to bag, you should go back to drinks, not to the home page
• Two people did not notice the menu tabs
• One user wanted a screen after adding item to bag that confirmed that the item was added
• Home page is weird

Positive…

• The do not disturb button
• The fact that the Home page is always available
• That the design is simple and pretty straightforward
• The illustrations responding to individual choices

So I performed some changes in my design:

• Changed the way ice/no ice can/no can options in the Coke screen are displayed. Instead of choosing between Ice/no ice now users only check the Ice box in case they do want ice. Added some description to the Item, clarifying that it is a 375ml can of the beverage.
• Changed the color of the words in the tabs to a darker tone of gray.
• After adding an item to bag, users are taken to the previous menu, not to the home.

This is how it looks like: