JFK uses the buggies for boarding when the gates are full. Last time I used one was in November '01 - the day the AA A300 crashed into the bay. We were already a couple hours late getting back from FCO and then the buggy de-planing through the back added an hour to my arrival time (and we were in BizE, too). At least the crew were on the buggy with us so I was able to get an explanation once I confronted them about that crash.