Shares in discount carrier Deccan Aviation began trading on Monday at a 22 per cent discount to its initial public offering price.At 9:56 am, the stock was at Rs 112 on the BSE after opening at Rs 115 in a weak Mumbai market, with 155,138 shares changing hands.The company raised Rs 3.63 billion, selling 24.55 million shares in the IPO at Rs 148 a share.