I was flying out of JFK on Monday, Jan 15 in the evening. Departures were on 22R. Since it was in the midst of the evening bank of departures, we had a good 45 minute wait. However the taxi procedure was different from what I've experienced at JFK (I was on UA Express).
We taxiid (sp?) out onto 13L with some aircraft while other aircraft went onto taxiway C. We got in line and sat in one position for a good 20 minutes while aircraft on C advanced forward, seemingly even ones that joined the line after us.
Then, we finally advanced and our entire group of aircraft took off. As we advanced toward 22R, we passed the other aircraft that joined after us (they were simply holding further ahead on C).
Anyhow, I've never noticed a long hold like that while a group advances. is this usual for departures on 22R? I've usually left on 31L. Perhaps it conserves fuel?