Hi guys.

As these photos show, you can really see the difference between a 747-400 Cargo plane that's clean and one that's dirty with stains.

View Large View Medium Photo © Ven Stephan

View Large View Medium Photo © Nathan Zalcman - AirTeamImages

My questions are about the KLM 747 with all the stains that are streaking back from the windows and doors and especially the cargo door seal on the nose.

What has caused these stains?

Is it dirt & dust from the load inside the 747's cargo hold that's leaking out through tiny holes in the fuselage due to cabin pressurization?

Or is it simply a matter of dirt & dust in the low altitude levels of outside air that the 747 is picking up along small body protrusions during it's arrival and approach to an airport?

View Large View Medium Photo © Nick de Jonge

View Large View Medium Photo © Ivan Coninx - Brussels Aviation Photography

I think these stains are more likely being caused by dirt in the polluted outside air that surrounds most major cities ...... because the angle of the long stains tend to indicate a nose up pitch attitude like that which would be used on approach for landing. Also, I'd be surprised to learn that a 747's fuselage could have that many pressurized air leaks.

I still wanted to ask this question to find out the answer for sure.


Thanks,

Chris