An Air India Airbus A320-200 aircraft takes off from the Sardar Vallabhbhai Patel International Airport in Ahmedabad, India, on July 7, 2017. —ReutersNEW DELHI: Air India expects to face around $600 million in additional costs if a ban from Pakistan’s airspace lasts for a year, and has asked the federal government to compensate it for the hit, a company letter seen by Reuters shows.Indian airlines are bracing for higher fuel costs and longer journey times after Pakistan shut its airspace...