You may have seen what seems to be a very shiny duct tape affixed to a part of the plane before, during, or after your flight…
For airlines, this silver tape is the equivalent of “sticky notes”.
If someone notices a hole or crack in the aircraft skin, or if some parts are at risk of falling off, but the plane is scheduled to take off before the repair can be completed, they will use silver sticky tape to hold the plane together or mark the spot where repair work needs to be done.
Silver is used because most aircraft have a silver base color.
If the plane makes it to its destination, the ground crew will see the silver “sticky note” and immediately begin work on the body repair so that most of it can be completed by the time the aircraft is due to take off again.
Officially, it’s called “speed tape”.
Speed tape can also be used to cover fresh sealing putty to protect it while curing. This sealant is purely aerodynamic to smoothen the surface, but, depending on the ambient temperature, it will take up to several days to get hard.
This ensures that the airplane can be used during this time, the fresh sealant gets covered with speed tape to prevent it from getting blown away by the slipstream.
Speed tape may even be used for other purposes such as temporarily attaching a partially detached stainless steel rub strip on top of the flap (when the flap is retracted, it touches the spoilers in this place. The rub strip prevents the spoiler from eating into the flap. The rub strip is simply glued on with adhesives).