It's easy to do. If you need to edit details / delete a flight which is on the trip, you need to split it and then edit each flight. See more here how can you split trips.
iOS
Edit trip name
Swipe trip left and tap on the blue button.
Rename it
Edit flight details
Swipe flight left and tap on the blue button
Then you can edit flight details (as well as its name)
Android
Edit trip name
Tap and hold the trip, then select the Edit button.
Rename it
Edit flight details
Tap and hold the flight, then select the Edit button.
Then you can edit flight details (as well as its name)
