My understanding is that people with young children will usually have APTA.
People with older children will usually get PTAP.
Adults traveling solo can expect to get TAPT.
But, since sometimes there are a lot more people with children than singles, or tons of older children, or it seems like nothing but couples - don't count on any certain rotation.
(Our kids are 4 and 5 - we are expecting APTA - might end up with PTAP - and I'd be shocked to get TAPT - but it could happen).