During World War II, pilots on US aircraft carriers adopted the thumbs up gesture to alert the deck crew that they were ready to go and that the wheel chocks could be removed. On modern US carriers, certain deck crew hold a thumb up to signal to the pilot and control tower that their station is OK for take-off. American GIs are reputed to have picked up on the thumb gesture and spread it throughout Europe as they marched toward Berlin.[5] According to Luís da Câmara Cascudo, Brazilians have adopted the thumbs up from watching American pilots based in northern Brazil during World War II.[9]