[Utopia]

smoke coming out of the plane before it hit

The smoke could simply be one of the engines on fire. It was a twin engine plane.

[Shermy]

Smoke could have been because the pilot was misusing the plane, his aim to crash into the building, not airplane maintenance. He called an SOS because he thought he might have to abort, had second thoughts and knew he could get to the target.

[Cold Heat]

The smoke could simply be one of the engines on fire. It was a twin engine plane

How about throttles forward to the stops and full rich mixture.