Heathrow in London is going to start using full body scanners on some passengers.
They can see through clothes, making it easier to search for things that might be dangerous.
Not every person will be scanned - the machines will only be used if there are concerns about a passenger.
They're part of new security measures to make flights safer, after a man tried to blow up a plane in America on Christmas Day.
The machine has been used at Manchester Airport's Terminal 2 since October, but not all airports will have them.
Some people say they aren't very good.
Some experts reckon they might not have been able to detect the bomb allegedly used in the attack on Christmas Day.