Just for some numbers for you to crunch, but if you are hired at Airtran in spring of 2007, you will be around #1500 on the seniority list. If nothing changes between now and 2011 (ie Midwest Merger, aircraft delivery slot deferring, or aircraft delivery slot sale), we will have 185 airplanes on property (87-717 and 98-737). Airtran typically has about 5-6 Captains per airplane. So by 2011, we will need about 1000-1100 Captains. Typically upgrades occur with about 60-80 First officers senior to you. So for a new hire in 2007 to make captain in 2011, you need to have 400 people senior to you leave. You will have lots of people senior to you leave your first and second year but that number will slow down in year 3 and beyond (I only moved up 9 numbers on the last seniority list, 7 of which were retirements and I have been here around 3 years).
If I was looking to come to Airtran in early 2007, I would expect 5 to 6 year upgrade when trying to determine if Airtran was a good fit for me. Just my $0.02.