The Hood's helicopter was, as the name suggests, a helicopter owned by The Hood. It was probably brought by the Hood from a military organization, or modified by him for his own purposes.
The Helicopter only appears in the movie Thunderbirds Are Go.After the Hood (in disguise as one of Zero X's mission scientists) has been unmasked by Scott, he makes an escape from Glenn Field Control Centre. He drives off in a car (pursued by Lady Penelope and Parker in FAB 1), towards a lake, where he then flees in a speedboat. Angry that Lady Penelope and Parker have used FAB 1's hydrofoils to follow him across the lake, the Hood ditches his speedboat for the helicopter, which is piloted by an unseen accomplice.
The helicopter tries to shoot at FAB 1 with its inbuilt machine guns, but Parker then fires FAB 1's grille-mounted cannon at the helicopter, causing it to fall into the sea and promptly explode, apparently killing the Hood and his accomplice.
However, the Hood might have survived the crash and subsequent explosion and returned as Black Phantom.