The best 'landed by itself' story I've read concerned, of all things, a U-2.
The pilot had an embolism, and conked out.
The a/c set off earthward and despite the best efforts of other plots sent up to help, the pilot remained on board, but unresponsive.
The a/c had a wing low and looked set to cartwheel on impact, but at the last moment flew through some HT wires which hooked a wing and set the U-2 nicely wings level.
It then landed itself gently, but split a fuel tank, the contents of which ran neatly away down a hill without going on fire.
The a/c sat there for a while, with the engine running. The pilot woke up and decided to disembark, but in doing so he fired his ejection seat.
The seat made him do a somersault, chipping one of his teeth, before thudding back into the ground beside him.
The Dragon Lady was returned to service, and I think, has survived.