airway primary cells stop growing at passage 3 - (Nov/12/2012 )

Dear all, I have faced a problem with my airway primary cell that: at passage 3, the cells look very healthy on the first day; The days after, the number of living and healthy cells seems to be unchanged while the number of dead cells increases (cells detach; debris appears). I kept changing medium to wash the dead cells out, but after 1 days, dead cells start appearing and increasing. The strange thing is that the healthy cells are still there but do not increase. This is the first time I have worked with primary cells so I am very confused with this problem.
Could somebody had the same problem and experience before?

How confluent are the cells? It sounds like they are contact inhibited and dying because of that.

Are they really passage 3 - as in you extracted them from the epithelium and have split them 3 times? or is it 3 passages since you thawed an aliquot? If it is the last option, have a look for information on the "Hayflick limit".