Planes flying along with siphons are bad example to ask theoretical physicists - most of them wouldn't be able to give you the right answers. Feynman was closer than most because he did think about things like what would happen if a rotating sprinkler sucked in water, etc.
All you need is very rudimentary fluid dynamics, some vague idea of attack angle, and the conservation of momentum with a compressed column of air under the plane. I think most theoretical physicists could come up with that.
The siphon one is funny because many people will start with air pressure, which is wrong. I'm wondering if you have some experience asking people these questions?
