My airline recently started a policy of not allowing seniority accrual for new-hires who have not completed training. I think this may be legal based on how they categorize new-hire trainees (ie, not as regular employees). In light of that it might be prudent to plan on completing training (including consolidation) to ensure seniority accrual.

They got tired of folks leaving AD, showing up just long enough to get a seniority number and then going on long-term orders before ever flying the line. Some of these folks never intended to return, but pocketed the seniority number as a fallback option in case plan A didn't work out down the road.