So you want to study on the tube or on the plane? Don't worry! This is totally possible.
Just make sure you download the content of your unit before you hop on the plane or train.
When you open your app, just click on the arrow at the top right and wait for your unit to download. Once the download is completed you can start learning.
Next time you have internet connection your progress will be synchronised so you don't have to worry about losing your progress.
Happy studying!