MONTREAL — More than a thousand passengers were affected after Air Canada partially suspended service to India due to the closure of Pakistani airspace as tensions mount between the two nuclear powers.A flight en route to Delhi Tuesday night turned back over the Atlantic Ocean and returned to Toronto Wednesday, the airline said.A second Air Canada flight from Vancouver to Delhi slated for takeoff Tuesday night was also cancelled, said spokeswoman Isabelle Arthur.Wednesday night flights on the same two same routes were cancelled “as there currently are no suitable alternate routings,” she said in an email.On both routes, Air Canada flies Boeing 787-9 Dreamliner jets that contain more than 280 seats, meaning up to 1,100 people are likely impacted by the cancellations so far.“We continue to monitor this situation closely and flights to Delhi will operate as soon as operationally feasible,” Arthur said.On Wednesday, Pakistan’s military said it shot down two Indian warplanes in the disputed region of Kashmir and captured a pilot, responding to an airstrike a day earlier by Indian aircraft inside Pakistan and raising tensions between the nuclear-armed rivals to a level unseen in the last two decades.The downing of the Indian aircraft came on a chaotic day that also saw mortar shells fired by Indian troops from across the frontier dividing the two sectors of Kashmir kill six civilians and wound several others.The closure of Pakistani airspace interrupted flights around the globe, as airlines scrambled to arrange refuelling stops.Emergencies — military, political and natural — ground flights periodically, said Kamran Bokhari, director for strategy and programs at the Centre for Global Policy in Washington D.C.“Recall the Malaysian flight shot down by Ukrainian rebels,” he said, referring to a deadly incident near the Russian border in July 2014. “They used one of those anti-aircraft systems and they locked onto it and the entire aircraft perished,” he said.Days later, the U.S. Federal Aviation Authority imposed a ban on American flights to Israel amidst Israeli airstrikes in the Gaza Strip. Air Canada resumed flights between Toronto and Tel Aviv after two days.While flight bans are typical in times of escalating conflict — in Syria in 2015, and across the U.S. after the 9/11 terror attacks, for example — “this is a game-changer to the historical policy of restraint by India,” Bokhari said. “Both sides are in undiscovered country.”In 2017, Saudi Arabia and Bahrain banned Qatari aircraft from flying through their airspace amid a diplomatic crisis precipitated by a blockade by five Middle Eastern states against the Qatar, choking Qatar Airways.In 2010, plumes of volcanic ash prompted the cancellation of thousands of flights when officials closed European airspace for five days, leaving tens of thousands of passengers stranded in one of the largest flight disruptions since the Sept. 11 attacks.Air Canada has implemented a “goodwill policy” for affected customers and is monitoring the situation in order to resume service once it “normalizes,” Arthur said.Canada’s largest airline operates daily service from Toronto and Vancouver to Delhi and four times weekly between Toronto and Mumbai. It has no aircraft on the ground in India and all flights from India to Canada have returned as scheduled, she said.A flight from Toronto to Mumbai was on track for takeoff Wednesday night, as the route avoids Pakistani airspace.Companies in this story: (TSX:AC)— With files from The Associated Press.