I am waiting for my parcel since a pretty long time. It said "posted" and now it says "sent to airline". First of all what does this status actually mean??

Also, in the meanwhile I had to change my mobile number .. I hope this does not affect the shipment. Do they contact me on my mobile number to arrange the shipment? I am afraid they tried to do so, did not reach me, as they still have my old number and now they are returning the parcel?!

Can I somehow update my mobile number? And even the address in the system??

http://track-chinapost.com/startairmail.php shows the number RN849386652CN was sent to airline on Mar 12.
China Post will lost control of the parcel after sent to airline. so there will be no update anymore after sent to airline date.

Sent to airline does not mean you will get the parcel very soon. It will keep waiting 5 to 10 days in airline warehouse waiting flight space and another 1 to 4 weeks import customs processing in destination country(speed depending on country). The status will stuck at "sent to airline" during this 2 to 6 weeks period.

Once it passes import customs clearance, UAE Post will scan and update its new location for China Post database and you will see new status.

PS: Mobile phone is useless in delivery. so no need change mobile number. Actually you can not change anything when parcel is on route. Remember to keep tracking your parcel in UAE POst website, UAE post will NOT make delivery, you need pickup the parcel from your P.O box in your local UAE post office.