I can't get past the biplane puzzle. First I slow down, open the top, speed up, get into position, and wait for the plane. Every single time I do this, Mabel slips and I have to rescue her. She mentions something about "getting it right", but I'm not sure what that means. Once the plane comes, I can't interact with the controls. And after getting the plane into position, Mabel doesn't give me any hint about what I need to do to keep her from falling off.
Is this a bug, or am I just missing something?