It might look like a prank, but it's not. Maintenance crew from Alaska Airlines cut out part of a Boeing 737's wing and wrote "We know about this" next to it. The aeroplane was then cleared for flying.
Imagine being a passenger on that plane and seeing the missing part along with the message. The plane was evidently OK to fly, since the pilots always inspect their aircraft before a flight for any reason to not take off. If I was on that plane I would wonder where else "we know about this" was marked. And then I would probably freak out.
The message could have been a way to reassure passengers, but an alleged Delta employee on Reddit claims that this practice is used to reduce paperwork:
I work for Delta in operations. This is for the ground personnel meeting the arriving aircraft (parkers), who are required to inspect the ship and document any damage found on arrival. Marking apparent damage prevents reports from being filed at each station at which the aircraft arrives. Delta does not do this and we inefficiently file a report tens of times for damage that has already been documented, creating needless redundant emails and work.
In the same thread, a military aeroplane mechanic confirms the maintenance paperwork nightmare:
I never worked civilian side but I worked F-16s and A-10s. We had so many writeups for planes we have a special form where writeups go to sit until there is sufficient downtime. Not to mention a pile of writeups of stuff that's currently "being worked." Then you have your engine fan blade map, dent map (for the wing/fuselage/tail) and I'm sure I'm forgetting something.
Alaska Airlines has apologised on Twitter. They admit the message was "inappropriate" and claim that they are "following up" with employees and passengers to see what happened. It seems that it may be normal practice. The only difference is that it was caught on camera this time. [Reddit via FlightGlobal]