Like anything else it depends on the airline. I was with a regional had a family emergency was given a leave for X period of time. That time ran out and I chose to resign (probably could have pushed for more time but how much time is too much to expect?) I did not see an end in sight so I left. 5 months later all was well I started sending out applications again and contacted the old company. They skipped right over the Interview and hired me back. I was brought in had all the paperwork to fill out all the background checks done again and given a new class date. (you have to re-do all the training through IOE)

Had to start seniority again but hey in a couple of years it wont matter.....kept the old number though which is good fo those surley old captains who hate "new" guys...

be up-front be truthful and ask everyone......theyll work with you I bet!