It has been strange because according to what I read, the PIC (Pilot in control) mainly conducts the ac functions so controlling while the pilot on the right side (usually) talks to the ATC.
However, I've seen this a few times on CX or KE but the PIC and the one talking changed.
For instance this is some conversation that I heard:
ATC: Korean xxx taxi into position and hold
KE: Korean xxx taxi into position and hold
ATC: Korean xxx cleared for take-off
KE:Cleared for take off Korean xxx
And the the plane is airborne
Then on the departure frequency, the pilot changes all of a sudden and says Korean xxx passing 1500 for 16000.
It was an obvious change because the pilot before take-off was Korean while the pilot after take-off was probably Caucasian based on the English I heard. The same thing happened on CX. They were approaching and it was a British pilot, and then when they were cleared to land, they were American. So does this swip-swap with pilots happen frequently?