The Mini Cooper driver, aged in her 40s, is pronounced dead at the scene.
An AAIB report says the plane was running at high power when it hit the Fowlmere airfield building.
The list for the RIBA awards includes a converted telephone exchange and a reimagined 80s bungalow.
The trial gives "our iconic postboxes a new lease of life", says Royal Mail chief Emma Gilthorpe.
Keeley has already raised thousands for charity by donating her hair and is about to cut it again.
The 100ft (30m) tunnel is only accessible through a trap door in the Grade II-listed house.
Sgt Russell Jones from Hertfordshire Police was riding his own machine when he crashed.
The 36-year-old male motorcyclist died at the scene, police say.
The pilot miscalculated his approach to the runway and ended up in foliage, a report finds.
