pilotss has the right answer. Pilots look at all the obvious surface issues of flying for a certain airline but often foget to check the balance sheet.
Check the debt/equity ratio that an airline has and consider long term job security while you are doing that. I recall a couple of guys leaving SWA in 2000 and 2001 for UAL and then after 9-11 calling SWA in near tears asking if they could come back. (They were told they could re-apply). SWA's debt/equity ratio is below 30% while many other airlines, INCLUDING those who recently went thru bankruptcy are over levereged with debt/equity ratios of over 100%.