I added this

model = FasterRCNN(backbone, num_classes=2) # Aircraft + background
…
…
pred = model(img)

And this is what i get

RuntimeError: Expected 4-dimensional input for 4-dimensional weight 1280 1280 3 3, but got 2-dimensional input of size [1, 1000] instead

img has the next shape : (1, 3, 920, 1080)