By Abhijith Ganapavaram, Aditya Kalra and Aditi Shah NEW DELHI (Reuters) - Top Indian airlines Air India and IndiGo are bracing for higher fuel costs and longer journey times as they reroute international flights after Pakistan shut its airspace to them amid escalating tensions over a deadly militant attack in Kashmir.

Indian airlines may suspend flights to a few destinations where it may be operationally or financially unviable to operate flights that circumvent the Pakistani airspace, according to industry experts.

In response to the April 22 terrorist attack in Pahalgam that claimed 26 lives, India on April 23 took a series of strong diplomatic and strategic measures. These included closing the Wagah-Attari border, suspending the Indus Water Treaty, and declaring all Pakistani nationals, including diplomats and defence personnel, persona non grata.