Red threads on wings
Flying in an Alitalia MD80 I noticed three yellow triangles with red threads on the wing, similar to those used on sailboats to check the trim of the sail.
Can't imagine what they're for, especially because to check them, the pilots would have to lean outside in flight, something Alitalia pilots would never do as it would mess up their hair.
Can anybody enlighten me on the use of these strange things?