This question already has an answer here:
Whilst flying into London's Stanstead Airport the other day I noticed that despite there being many jetways available Ryanair weren't using them for any of their planes. Instead, they'd chosen to have pairs of staircases at either end of the plane. The same is also true when they are operating out of other airports where jetways are available.
Is this just done for speed or might there be other reasons for making this decision?