Simply put, it varies greatly. However you should realize that the airlines you named aren't considered entry level jobs. In fact if you are able to get to one of those companies within 6-8 years after graduating college, you are probably doing pretty well with your career.

Look at the regional airlines instead which are considered "entry level airlines." You'll spend several years at one of those carriers flying turboprop or small regional aircraft (like the Canadair Regional Jet). First as a First Officer, then as a Captain. Once you have a year or two under your belt as a Captain, you will most likely meet the qualifications that major airlines are looking for (generally 5000+ hrs total time and 1000+ hrs as a Captain put you in the range.)

Starting pay at the regionals varies, but generally is between $19,000/year and $25,000/year. After the first year it will increase to the $25k-35k zone and then makes small increases (about 3% a year) until you upgrade to captain. Regional captains make around 45-60K a year their first year as captain and can make as much as about $100-105K if they have been with the company for an extended period (15+ years).