Depending on budget of project.
Large budget -
Most high end productions can rent a specific model of craft (hero craft, tight shots, flying), and buy a secondary (rebuild) and retro fit to RC like a radio controlled toy, or third (non functioning from graveyard). Secondary and thirds have cosmetic work done to look like hero. Most explosions are dropped with cables, off cranes, or actually on ground and exploded. Radio controlled are very costly.
Models and CGI
High end models are made of the crash scene, and the model plane to crash. If the modelers are good, this blends very well. If not, you can see the variance (James bond series has a few plane crashes done in the past that don't look quite right)
CGI and CGI model blends have improved so much it is difficult to differentiate between them and actual shots. (again pending the quality of artist and software.
I stress no real plane is crashed with a human inside.
Smaller budgets use stock footage.
Many stock footage companies now will take a hero plane (common type of craft), and R/C control a secondary (flying condition), and crash and explode it in a field. This stock footage is edited to clear back ground option.
I personally worked on set with a helicopter crash. A rented helicopter was used one day to fly down a street and shoot machine guns at a limo. That scene cost $30,000.00. The balance of helicopter footage was stock footage, and the crash was stock footage and CGI. Still was a great piece.