Mumbai: Salman Khan-Katrina Kaif starrer 'Tiger Zinda Hai' is well on its way to becoming a blockbuster with earnings of over Rs 150 crore in its first four days, trade sources said. The film, which has already set a record for the highest opening weekend ever for a Bollywood film with collections of Rs 114.93 crore in its first three days, continued its strong run at the box office on Monday with collections of over Rs 40 crore on Christmas day.The film has thus earned over Rs 150 crore in just four days.