Complex sentence: After some time, he migrated to Calcutta (now Kolkata) and joined Indian Airlines under sports quota as he was a skilled hockey player also and in fact played for Allahabad University and had been selected for the nationals as standby.
Split into simpler sentences: After some time, he migrated to Calcutta (now Kolkata) and joined Indian Airlines under sports quota; as he was a skilled hockey player. He played for Allahabad University and had been selected for the nationals as standby.