This paper investigates the time-complexity of the non-blocking atomic commit (NBAC) problem in a synchronous distributed model where t out of n processes may fail by crashing. We exhibit for t > 3 an inherent trade-off between the fast abort property of NBAC, i.e., aborting a transaction as soon as possible if some process votes ``no,'' and the fast commit property, i.e., committing a transaction as soon as possible when all processes vote ``yes'' and no process crashes. We also give two algorithms: the first features fast commit and weak fast abort, whereas the second features fast abort and weak fast commit.