I learned Morse by sound, not by dots and dashes on a sheet of paper. Began with my amateur radio licence, then did a Marine Operator's Certificate and finally managed to read 28 words per minute fluently. Mostly at sea we used speeds in the range of 16-18wpm.
Morse and music have much in common. A musical pitch, speed, rhythm, a beat, even certain passages of morse become as familiar as the opening bars of your favourite pieces of music. I haven't used Morse for over 12 years now, but even now I can remember the opening Morse for a Sydneyradio traffic list on 476Khz. You didn't read individual letters, it was just a long string of familiar characters that were always the same which preceeded the traffic list. Unforgettable.
So, to learn morse, learn it as an aural language, as if you lived in a country where Morse was a spoken language and you heard it all day, every day. Steep yourself in it and it will sink in and you won't be able to stop it. I used a HF communications receiver tuned to the 8Mhz marine band and listened whilst I was washing dishes, so my wet hands couldn't write down the characters, I had to learn to read them in my head. That works. For aviation you only need very slow Morse, so it shouldn't take too long.
There was a great little device back in the 1980s called the Datong Morse Tutor; a pale blue plastic box which generated random five-letter or mixed letter-number groups at any speed desired at the turn of a knob.The radio amateurs lapped them up. If you can find one they are a real help to learning the code. These days it's getting very hard to find Morse on the HF bands, although the mainland Chinese coast stations still come through on 8Mhz at night, here in Australia.