Mumbai, March 22 -- Pakistan's airspace curbs for commercial flights since 27 February following the border row with India, have kept the Army on high alert, while airlines operating in India battle a sharp rise in operational expenses. Pakistan Civil Aviation Authority on Monday extended its restriction on airspace for all overflying (transit) flights till Tuesday. The civil aviation regulator has been extending the curbs frequently since the border flare- up. Only Pakistani airlines and some Gulf airlines flying to Pakistan have been allowed to use the airspace. The curbs have led other airlines, including Indian companies, to cancel several flights and take longer routes, adding to their operating expenses. "We are waiting for Pakistan t...