Originally Posted by gooselee

Short story: as other posters have said, if your friends set up their own FF accounts, it's a simple call to add their # to the PNR. You may even be able do this at the check-in counter or gate without blinking (DL will actually let you set up a new SkyMiles account and add the current flight on board while in air). But the FF# should match the passenger, not the purchaser.