I sometimes open "Live ATC" app on my iPhone and listen to the "status" of my airplane when I'm taking off until my plane reaches the runway (I know the phone have to be turned off but its exciting to listen to ATC communicating with your pilot). In order to know the status, I have to know the call sign of the plane. If I'm taking off from a small airport, I kinda guess the call sign based on the conversation between the ATC and the pilots and the position of my plane (for example if the ATC says United 220 hold short of Juliet and if my plane is on Juliet, I know my plane is United 220). There have been times when the pilot announces the call sign of the plane before pushback. My question is, Is it okay or weird for me to ask the call sign of the plane to the pilots / flight crew.