Two helicopters collided while trying to land below Mount Everest base camp on Tuesday, killing a 47-year-old Indian tourist and injuring two other people, officials in Nepal said.

The crash happened in Pheriche village at an altitude of 4,200 metres (13,780 feet), just below the South Base Camp. Footage posted online showed more than a dozen people running for safety as the aircraft hit the ground after the collision.

A New Zealand national and a Nepali pilot were injured, according to Al Jazeera. The New Zealander was being taken to Kathmandu for treatment, ABC News reported. It is not yet clear how many people were on board the two helicopters.

Both aircraft were ferrying trekkers who had been hiking to the base camp during one of the busiest seasons for the route, ABC reported, citing officials from the Solukhumbu district.

Why landings there are hard

Pheriche sits on the main trekking route to Everest base camp and is used as an acclimatisation stop. At 4,200 metres, the air is thin enough that helicopters lose lift, and the terrain offers little space for a second approach if the first one is aborted.

The Everest region has no radar coverage comparable to a commercial airport, and traffic is managed largely by radio and by the pilots' own separation. In peak season, dozens of helicopter flights a day move climbers, trekkers and supplies between Lukla, Pheriche and base camp.

Weather adds another variable. Heavy snow had covered the route before conditions improved on Sunday, allowing thousands of trekkers to move around, according to ABC. A sudden improvement in weather can concentrate flights into a short window, which is exactly when separation matters most.

The tourism pressure

Nepal's Everest region depends on trekking and climbing, and the autumn season is one of the two busiest periods of the year. Helicopter transfers have become a standard part of the business: they evacuate sick climbers, move supplies and offer short sightseeing flights to base camp for visitors who cannot make the multi-day walk.

That volume has grown faster than the infrastructure that supports it. Landing sites are informal, radio procedures vary between operators, and the regulator's oversight is stretched across a huge, difficult terrain.

The crash will renew questions about how helicopter traffic around the world's highest mountain is managed, and whether the number of flights should be capped during peak periods.

What happens next

Nepal's civil aviation authorities are expected to open an investigation into how the two aircraft came to attempt to land at the same place at the same time. The operator of one of the helicopters confirmed both passengers were tourists.

Bodies and injured passengers were being moved down the valley, a process that is itself slow at that altitude and often depends on further helicopter flights.

For the families involved, the investigation will matter more than the policy debate. For the industry, the question is whether the season's remaining flights proceed under tighter separation rules or whether operators will be asked to pause and review.

The crash is the latest reminder that the Everest region's appeal and its risk come from the same thing: a landscape that is spectacular, crowded and unforgiving.

Altitude is the reason the margin for error is so small. At 4,200 metres the air is thin enough that helicopter engines produce less power and rotors generate less lift, so a landing that would be routine at sea level becomes a manoeuvre with little reserve. Pilots also have less room to abort: the terrain rises on most sides and the approaches are short.

Nothing in the accounts so far explains why both aircraft were attempting to land at the same time. That is the central question for investigators, and it is one that radio logs and the helicopters' own recording equipment should be able to answer. In the meantime, the season continues: thousands of trekkers are still on the route, and the flights that supply and evacuate them will keep operating under whatever separation rules the authorities impose.

Beyond the immediate investigation, the crash raises a question about growth. Helicopter tourism has expanded because it is profitable and because it answers a real need: rapid evacuation and access for people who cannot walk for days at altitude. Enforcement is the hard part. Rules that look sensible on paper are difficult to apply on a mountain where weather changes by the hour and landing sites are chosen by pilots on the spot, with limited oversight from the ground. That is why the investigation's findings will matter beyond this week's flights and beyond this season, for every operator flying into the same crowded valley and every trekker booking a flight on it.

Aviation and mountain emergencies have been in the news this week, from the mid-air helicopter collision in Oregon to the fatal high-speed train crash in Spain, and rescuers have also been stretched by this autumn's flood watch in Hawaii.