Are you referring to wide body aircraft? If so it probably has to do with whether the aircraft is configured for domestic or international flights.

When TW was flying L-1011s the planes configured for international flights started with row 2, those configured for domestic flights started with row 1. The difference? The domestically configured aircraft had business class seating configured in a 2-4-2 seating arrangement (hardly business class as I prefer to know it). The internationally configured aircraft had business class seating of 2-2-2. In both cases there was also a first class section. While you never saw a domestically configured aircraft on an international run, it wasn't uncommon to see an internationally configured aircraft on a domestic run.

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Robert Johnson
danville 1K