an sms is all it takes
Just before leaving abroad, using your India airtel SIM, send SMS "AWS A" to 58125 to activate your service. This would instantly activate your airtel world sim^TM. However, please note that you would be unable to use your India airtel SIM once your airtel world sim^TM is activated, hence activation should be done just before departure.

• If you would like to activate the airtel world sim^TM at a particular time then send the following sms “aws a hh:mm”. You would need to specify the time (IST) at which you want the service to be activated in hh:mm format. On successful activation, you would receive a confirmatory SMS.

• For example, if your international flight is at 10:20 pm , then prior to your departure send an sms “AWS A 22:20” to 58125. Note: Once the service is activated, you would be unable to receive any calls on your India airtel SIM.