But right there amid the super-sized jets and modern technology at Chicago's O'Hare International Airport you can find a group of goats, sheep, llamas and wild burros.
Their main job is to eat up the grass on parts of the airport where lawnmowers can't - or shouldn't - get to.
One official calls it "Project Herd" - part of a series of environmental initiatives carried out at the airport.
Besides keeping the growing grass at bay, the animals are also used to rid the airport grounds of habitat for birds and other wildlife that can cause problems to aircraft taking off and landing at the airport.
For example, the llamas and burros scare coyotes away - in the case of burros, they simply stomp coyotes to death.