Kathmandu, March 7 -- Cancelled flights and postponed trips triggered by the war in the Middle East have cast deep uncertainty over Nepal's tourism outlook at the start of the peak spring season.

"This is the start of the high season here. It's catastrophic," said Mandip Giri, managing director of Dom Himalaya Hotel in Chettrapati, on the western edge of Thamel. "We had 90 percent occupancy till Sunday. Now it has dropped below 50 percent."

According to Giri, booking cancellations have reached more than 70 percent. "Some have postponed their trips, but we are not sure they will come."

Spring is the peak season when tourists arrive in Nepal for trekking and mountaineering, and hotels are usually close to fully booked during this time of...