When I made a flying machine with observer blocks, I thought It would just fly and keep on until I stop it.
What happened instead was that it did fly, but it made ghost blocks (blocks that arent really there) from itself. That is very bad for making transporting through the air and on flying machines and so on.
This is what I did
1. (IMPORTANT: IT CANT TOUCH ANY BLOCKS!) Put a observer block looking away from a sticky piston. Put a slime against the sticky piston. To the left you do the same thing but from the other side so the sticky pistons are verticly touching eachother (by the pixles).
2. Put redstone torches on both slime blocks. The first one you put on the back slime block and the second on the front slime block. Then break the one at the back and then the one in the front. Do the opposite to go backwards.
3. Let it fly for a while and you will start to see what I mean.