It's very easy.
iOS
Swipe left on the flight you want to delete.
Then tap red button to delete.
Android
Tap and hold the flight you want to delete. If it's a one-leg flight, you would see a delete button at the top right-hand corner.
If its a multi-leg flight, tap and hold, and then select the "3 dots" at the upper right-hand corner and select "delete".
Select "Delete".
